1.      Ghusl (complete bath) becomes obligatory in the following conditions:

a.      When Mani (fluid) is discharged owing to stimulation (whether actual or imagined) while asleep or awake.

b.      When a wet dream occurs for both men and women.

c.       When an actual intercourse takes place (even if no discharge occurs).

d.      When the private parts meet (even if no discharge occurs).

e.       When a woman comes out of her regular menstrual cycle.

f.       When the normal flow of blood ceases from the womb after giving birth.

http://www.askimam.org/fatwa/fatwa.php?askid=6fd595dcfb9c4d71ee0e26a79af452a3

‏حدثنا ‏ ‏عبد الله بن يوسف ‏ ‏قال أخبرنا ‏ ‏مالك ‏ ‏عن ‏ ‏هشام بن عروة ‏ ‏عن ‏ ‏أبيه ‏ ‏عن ‏ ‏زينب بنت أبي سلمة ‏ ‏عن ‏ ‏أم سلمة أم المؤمنين ‏ ‏أنها قالت ‏
‏جاءت ‏ ‏أم سليم امرأة ‏ ‏أبي طلحة ‏ ‏إلى رسول الله ‏ ‏صلى الله عليه وسلم ‏ ‏فقالت يا رسول الله إن الله لا يستحيي من الحق هل على المرأة من غسل إذا هي احتلمت فقال رسول الله ‏ ‏صلى الله عليه وسلم ‏ ‏نعم إذا رأت الماء

Narrated Um-Salama (RA) (the mother of the believers) Um Sulaim (RA) , the wife of Abu Talha (RA) , came to Allah's Apostle (Sallaho Alaihe Wassallam) and said, "O Allah's Apostle (Sallaho Alaihe Wassallam)! Verily Allah is not shy of (telling you) the truth. Is it necessary for a woman to take a bath after she has a wet dream (nocturnal sexual discharge)?" Allah's Apostle (Sallaho Alaihe Wassallam) replied, "Yes, if she notices a discharge." [Bukhari]

Yahya (RA) related to me from Malik (RA) from Yahya ibn Said (RA) from Said ibn al-Musayyab (RA) that Abu Musa al-Ashari (RA) came to A'isha (RA), the wife of the Prophet (Sallallahu Alaihi Wasallam) and said to her, "The disagreement of the companions in a matter which I hate to bring before you has distressed me." She (RA) said, "What is that? You did not ask your mother about it, so ask me." He (RA) said, "A man penetrates his wife, but becomes listless and does not ejaculate. "She (RA) said, "When the circumcised part passes the circumcised part ghusl is obligatory." Abu Musa (RA) added, "I shall never ask anyone about this after you." [Muwatta Imam Malik]

وَيَسۡـَٔلُونَكَ عَنِ ٱلۡمَحِيضِ‌ۖ قُلۡ هُوَ أَذً۬ى فَٱعۡتَزِلُواْ ٱلنِّسَآءَ فِى ٱلۡمَحِيضِ‌ۖ وَلَا تَقۡرَبُوهُنَّ حَتَّىٰ يَطۡهُرۡنَ‌ۖ فَإِذَا تَطَهَّرۡنَ فَأۡتُوهُنَّ مِنۡ حَيۡثُ أَمَرَكُمُ ٱللَّهُ‌ۚ إِنَّ ٱللَّهَ يُحِبُّ ٱلتَّوَّٲبِينَ وَيُحِبُّ ٱلۡمُتَطَهِّرِينَ

[2:222] They ask you about menstruation. Say: ―It is an impurity. So, keep away from women during menstruation; and do not have intimacy with them until they are cleansed. But when they are cleansed, then go to them from where Allah has commanded you. Surely Allah loves those who are most repenting, and loves those who keep themselves pure.

وَإِن كُنتُمۡ جُنُبً۬ا فَٱطَّهَّرُواْ‌ۚ

[5:6] …If you are in a state of major impurity, cleanse yourselves well (by taking bath)…

2.      Ghusl (complete bath) does not become obligatory in the following conditions:

a.      If Al-Mani (fluid) is discharged without desire due to a medical condition, or carrying a heavy load or cold

b.      When prostatic fluid comes out

حدثنا ‏ ‏عبد الله بن مسلمة ‏ ‏عن ‏ ‏مالك ‏ ‏عن ‏ ‏أبي النضر ‏ ‏عن ‏ ‏سليمان بن يسار ‏ ‏عن ‏ ‏المقداد بن الأسود ‏
‏أن ‏ ‏علي بن أبي طالب ‏ ‏رضي الله عنه ‏ ‏أمره أن يسأل له رسول الله ‏ ‏صلى الله عليه وسلم ‏ ‏عن الرجل إذا دنا من أهله فخرج منه ‏ ‏المذي ‏ ‏ماذا عليه فإن عندي ابنته وأنا ‏ ‏أستحيي أن أسأله قال ‏ ‏المقداد ‏ ‏فسألت رسول الله ‏ ‏صلى الله عليه وسلم ‏ ‏عن ذلك فقال ‏ ‏إذا وجد أحدكم ذلك ‏ ‏فلينضح ‏ ‏فرجه وليتوضأ وضوءه للصلاة

Narrated Al-Miqdad ibn al-Aswad (RA): Ali ibn AbuTalib (RA) commanded him to ask the Apostle of Allah (Sallallahu Alaihi Wasallam) what a man should do when he wants to have intercourse with his wife and the prostatic fluid comes out (at this moment). (He said): I am ashamed of consulting him because of the position of his daughter. Al-Miqdad said: I asked the Apostle of Allah (Sallallahu Alaihi Wasallam) about it. He said: When any of you finds, he should wash his private part, and perform ablution as he does for prayer. [Abu Dawud]

‏
قال مجاهد: بينا نحن - أصحاب ابن عباس - حلَقٌ في المسجد؛ طاووس، وسعيد ابن جبير، وعكْرمة، وابن عباس قائم يصلي، إذ وقف علينا رجل، فقال: هل من مفْت؟ فقلنا: سل. فقال: إني كلما بُلت، تبعه الماء الدافق ؟ قلنا: الذي يكون منه الولد ؟ قال نعم. قلنا: عليك الغسل. قال: فولَّى الرجل، وهو يرَجِّع، قال: وَعجَّل ابن عباس في صلاته، ثم قال لعكرمة:عليَّ بالرجلِ. وأقبل علينا، فقال:أرأيتم ما أفتيتم به هذا الرجل عن كتاب اللّه ؟ قلنا: لا. قال: فعن رسول اللّه ؟ قلنا: لا. قال: فعن أصحاب رسول اللّه صلى الله عليه وسلم؟ قلنا: لا. قال: فعمّه ؟ قلنا: عن رأينا. قال: فلذلك قال رسول اللّه صلى الله عليه وسلم: " فقيه واحد، أشد على الشيطان من ألف عابد ". قال: وجاء الرجلُ، فأقبل عليه ابن عباس، فقال: أرأيت إذا كان ذلك منك، أتجد شهوة في قُبلك ؟ قال: لا. قال: فهل تجدُ خدَراً في جسدك ؟ قال: لا. قال: إنما هذه إبردة، يجزيك منها الوضوء.

Said Mujahid, "We were in a meeting in the mosque with the companions of Ibn 'Abbas (Tawus, Sa'eed ibn Jubair and 'Ikrimah). When he stood to pray, a man came in and said, 'Is there one who can give a legal verdict?' We said, 'Ask your question.' He said, 'Whenever I urinate, a liquid always follows it.' We asked, 'Is it the type of liquid that gives birth to children?' He said, 'Yes.' We said, 'Then you have to perform ghusl.' The man went away. Ibn 'Abbas hurried to finish his prayer, after which he told 'Ikrimah to bring the man back. He turned to us and said, 'Is your verdict found in the Book of Allah?' We said, 'No.' He asked, 'Is it based on the sayings of the Prophet, upon whom be peace?' We said, 'No.' 'Then from what?' We said, 'From our opinion.' He said, 'That is why the Messenger of Allah said that one learned man is more difficult for Satan than a thousand worshippers.' The man came and faced Ibn 'Abbas, who said to him, 'When that happens, is it owing to any stimulation?' He answered, 'No.' Ibn 'Abbas asked, 'Do you feel any numbness in your body?' He answered, 'No.' Said Ibn 'Abbas, 'That is from the cold. Ablution is sufficient."' [Tirmidhi]

3.      Ghusl (complete bath) is Sunnah and/or recommended in the following occasions:

a.      On Fridays.

b.      On Eid days.

c.       After giving Ghusl to a bier.

d.      Before putting on the Ihram.

e.       Before entering Makkah.

f.       Before entering Madina.

g.      Before commencing the stay of Arafah (during Hajj)

‏حدثنا ‏ ‏آدم ‏ ‏قال حدثنا ‏ ‏ابن أبي ذئب ‏ ‏عن ‏ ‏سعيد المقبري ‏ ‏قال أخبرني ‏ ‏أبي ‏ ‏عن ‏ ‏ابن وديعة ‏ ‏عن ‏ ‏سلمان الفارسي ‏ ‏قال ‏
‏قال النبي ‏ ‏صلى الله عليه وسلم ‏ ‏لا يغتسل رجل يوم الجمعة ويتطهر ما استطاع من طهر ويدهن من دهنه أو يمس من طيب بيته ثم يخرج فلا يفرق بين اثنين ثم ‏ ‏يصلي ما كتب له ثم ينصت إذا تكلم الإمام إلا غفر له ما بينه وبين الجمعة الأخرى

Narrated Salman Al-Farsi (RA): Allah's Apostle (Sallallahu Alaihi Wasallam) said, "Anyone who takes a bath on Friday and cleans himself as much as he can and puts oil (on his hair) or scents himself; and then proceeds for the prayer and does not force his way between two persons (assembled in the mosque for the Friday prayer), and prays as much as is written for him and remains quiet when the Imam delivers the Khutba, all his sins in between the present and the last Friday will be forgiven." [Bukhari]

استحب العلماء الغسل للعيدين، ولم يأت في ذلك حديث صحيح، قال في " البدر المنير ": أحاديث غسل العيدين ضعيفة، وفيها آثار عن الصحابة جيدة

Scholars also encourage Muslims to perform ghusl for the 'id prayers, even though there is no authentic hadith to support this opinion. The hadith concerning performing ghusl for the 'ids are weak. But there do exist good reports from the companions (on this point) [AlBadrul Muneer, Nailul Awtar]

أبي هريرة - رضي اللّه عنه - أن النبيّ صلى الله عليه وسلم قال: " من غسل ميتاً، فليغتسل، ومن حمله، فليتوضأ

الحافظ ابن حجر قال في حديثنا هذا: قد حسنه الترمذيُّ، وصححه ابن حبان،

Abu Hurariah (RA) reported that the Prophet (Sallaho Alaihe Wassallam) said, "Whoever has washed a corpse must perform ghusl, and whoever carried him must perform ablution." [Ahmed, Abu Dawud, Tirmidhi and others]

Al-Hafidh Ibn Hajr (RA) quotes Tirmidhi & Ibn Hibban: "Tirmidhi called it Hasan and Ibn Hibban called it sahih”.

زيد بن ثابت، أنه رأى رسول اللّه صلى الله عليه وسلم تجرَّد لإهلاله، واغتسل . رواه الدارقطنيُّ، والبيهقي، والترمذيُّ، وحسّنه، وضعفه العُقيلي

Zaid ibn Thabit (RA) related that he saw the Messenger of Allah (Sallallahu Alaihi Wasallam), when he intended to perform the hajj, perform ghusl. [Darqutni, Baihaqi, Tirmidhi who classed it as Hasan but Al-Usaili regarded it as weak]

روى عن نافع أن بن عمر كان لا يقدم مكة إلا بات بذي طوى ، حتى يصبح ويغتسل ، ثم يدخل مكة نهارا ، ويذكر عن النبي صلى الله عليه وسلم أنه فعله . رواه البخاري ومسلم .

Nafi' (RA) reported that Ibn Umar (RA) did not enter Mecca without spending the night at Dhi Tawu until it was dawn, when he took a bath, and then entered Mecca in the morning, and made a mention that Allah's Apostle (Sallallahu Alaihi Wasallam) did that.[Agreed upon]

‏و حدثني ‏ ‏عن ‏ ‏مالك ‏ ‏عن ‏ ‏نافع ‏ ‏أن ‏ ‏عبد الله بن عمر ‏
‏كان ‏ ‏يغتسل لإحرامه قبل أن يحرم ولدخوله ‏ ‏مكة ‏ ‏ولوقوفه عشية ‏ ‏عرفة

Nafi' (RA) ) reported that 'Abdullah ibn Umar (RA) used to do ghusl for ihram before he entered ihram, and for entering Makka, and for standing on the afternoon of 'Arafa. [Muwatta Imam Malik]

http://www.saaid.net/book/8/1668.zip

...ويغتسل قبل الدخول وبعده إن أمكنه...

4. Make the intention for Ghusl, “I am intending to purify myself”.

‏حدثنا ‏ ‏الحميدي عبد الله بن الزبير ‏ ‏قال حدثنا ‏ ‏سفيان ‏ ‏قال حدثنا ‏ ‏يحيى بن سعيد الأنصاري ‏ ‏قال أخبرني ‏ ‏محمد بن إبراهيم التيمي ‏ ‏أنه سمع ‏ ‏علقمة بن وقاص الليثي ‏ ‏يقول سمعت ‏ ‏عمر بن الخطاب ‏ ‏رضي الله عنه ‏ ‏على المنبر ‏‏قال سمعت رسول الله ‏ ‏صلى الله عليه وسلم ‏ ‏يقول ‏ ‏إنما الأعمال ‏ ‏بالنيات ‏ ‏وإنما لكل امرئ ما نوى فمن كانت هجرته إلى دنيا ‏ ‏يصيبها ‏ ‏أو إلى امرأة ينكحها فهجرته إلى ما هاجر إليه

Narrated 'Umar bin Al-Khattab (RA): Allah's Apostle (Sallaho Alaihe Wassallam) said, "The reward of deeds depends upon the intention and every person will get the reward according to what he has intended. So whoever emigrated for Allah and His Apostle, then his emigration was for Allah and His Apostle. And whoever emigrated for worldly benefits or for a woman to marry, his emigration was for what he emigrated for." [Bukhari]

Note: Intention doesn’t need to be uttered verbally or loudly, it is an action of the heart.

5. Wash your hands up to the wrists.

‏حدثنا ‏ ‏عبد الله بن يوسف ‏ ‏قال أخبرنا ‏ ‏مالك ‏ ‏عن ‏ ‏هشام بن عروة ‏ ‏عن ‏ ‏أبيه ‏ ‏عن ‏ ‏عائشة زوج النبي ‏ ‏صلى الله عليه وسلم ‏
‏أن النبي ‏ ‏صلى الله عليه وسلم ‏ ‏كان ‏ ‏إذا اغتسل من الجنابة بدأ فغسل يديه ثم يتوضأ كما يتوضأ للصلاة ثم يدخل أصابعه في الماء ‏ ‏فيخلل ‏ ‏بها أصول شعره ثم يصب على رأسه ثلاث غرف بيديه ثم ‏ ‏يفيض ‏ ‏الماء على جلده كله

Narrated 'Aisha(RA): Whenever the Prophet (Sallaho Alaihe Wassallam) took a bath after Janaba he started by washing his hands and then performed ablution like that for the prayer. After that he would put his fingers in water and move the roots of his hair with them, and then pour three handfuls of water over his head and then pour water all over his body. [Bukhari]

Narrated Maimuna (RA): (the wife of the Prophet) Allah's Apostle (Sallaho Alaihe Wassallam) performed ablution like that for the prayer but did not wash his feet. He washed off the discharge from his private parts and then poured water over his body. He withdrew his feet from that place (the place where he took the bath) and then washed them. And that was his way of taking the bath of Janaba. [Bukhari]

6. Wudhu should now be performed.

حدثنا ‏ ‏عبد الله بن يوسف ‏ ‏قال أخبرنا ‏ ‏مالك ‏ ‏عن ‏ ‏هشام بن عروة ‏ ‏عن ‏ ‏أبيه ‏ ‏عن ‏ ‏عائشة زوج النبي ‏ ‏صلى الله عليه وسلم ‏
‏أن النبي ‏ ‏صلى الله عليه وسلم ‏ ‏كان ‏ ‏إذا اغتسل من الجنابة بدأ فغسل يديه ثم يتوضأ كما يتوضأ للصلاة ثم يدخل أصابعه في الماء ‏ ‏فيخلل ‏ ‏بها أصول شعره ثم يصب على رأسه ثلاث غرف بيديه ثم ‏ ‏يفيض ‏ ‏الماء على جلده كله

Narrated 'Aisha(RA): Whenever the Prophet (Sallaho Alaihe Wassallam) took a bath after Janaba he started by washing his hands and then performed ablution like that for the prayer. After that he would put his fingers in water and move the roots of his hair with them, and then pour three handfuls of water over his head and then pour water all over his body. [Bukhari]

Note: If the surface where the person is standing is clean then feet can be washed at the same time (see Hadeeth narrated by Maumuna (RA) earlier)

7. You should now rub water through your hair three times, letting the water penetrate down to the roots of the hair.

حدثنا ‏ ‏عبد الله بن يوسف ‏ ‏قال أخبرنا ‏ ‏مالك ‏ ‏عن ‏ ‏هشام بن عروة ‏ ‏عن ‏ ‏أبيه ‏ ‏عن ‏ ‏عائشة زوج النبي ‏ ‏صلى الله عليه وسلم ‏
‏أن النبي ‏ ‏صلى الله عليه وسلم ‏ ‏كان ‏ ‏إذا اغتسل من الجنابة بدأ فغسل يديه ثم يتوضأ كما يتوضأ للصلاة ثم يدخل أصابعه في الماء ‏ ‏فيخلل ‏ ‏بها أصول شعره ثم يصب على رأسه ثلاث غرف بيديه ثم ‏ ‏يفيض ‏ ‏الماء على جلده كله

Narrated 'Aisha(RA): Whenever the Prophet (Sallaho Alaihe Wassallam) took a bath after Janaba he started by washing his hands and then performed ablution like that for the prayer. After that he would put his fingers in water and move the roots of his hair with them, and then pour three handfuls of water over his head and then pour water all over his body. [Bukhari]

8. You should now pour water over the head and the rest of the body three times starting from the right side.

حدثنا ‏ ‏عبد الله بن يوسف ‏ ‏قال أخبرنا ‏ ‏مالك ‏ ‏عن ‏ ‏هشام بن عروة ‏ ‏عن ‏ ‏أبيه ‏ ‏عن ‏ ‏عائشة زوج النبي ‏ ‏صلى الله عليه وسلم ‏
‏أن النبي ‏ ‏صلى الله عليه وسلم ‏ ‏كان ‏ ‏إذا اغتسل من الجنابة بدأ فغسل يديه ثم يتوضأ كما يتوضأ للصلاة ثم يدخل أصابعه في الماء ‏ ‏فيخلل ‏ ‏بها أصول شعره ثم يصب على رأسه ثلاث غرف بيديه ثم ‏ ‏يفيض ‏ ‏الماء على جلده كله

Narrated 'Aisha(RA): Whenever the Prophet (Sallaho Alaihe Wassallam) took a bath after Janaba he started by washing his hands and then performed ablution like that for the prayer. After that he would put his fingers in water and move the roots of his hair with them, and then pour three handfuls of water over his head and then pour water all over his body. [Bukhari]

9. No area of the body (even equal to a hair) should be left dry during Ghusl. If the hair of a woman is plaited then it is not a required to open the plait (loosening would be sufficient) provided that water reaches the base of each and every hair and nothing is left dry.

وَإِن كُنتُمۡ جُنُبً۬ا فَٱطَّهَّرُواْ‌ۚ

[5:6] …If you are in a state of major impurity, cleanse yourselves well (by taking bath)…

Note: Scholars have stated that the obligation of ensuring that all parts of the body are thoroughly washed is established from this verse.

وعن عُبيد بن عمير - رضي اللّه عنه - قال: بلغ عائشة - رضي اللّه عنها - أن عبد اللّه بن عمر يأمـر النساء إذا اغتسلـن، أن ينقضن رءوسهن، فقالت: يا عجباً لابن عمر، يأمر النساء إذا اغتسلن بنقض رءوسهن، أفلا يأمرهن أن يحلقن رءوسهن؛ لقد كنت أغتسل أنا ورسولُ اللّه صلى الله عليه وسلم من إناء واحد، وما أزيد على أن أفرغ على رأسي ثلاث إفراغات  رواه أحمد، ومسلم.

'Ubaid ibn 'Umair (RA) reported that 'Aishah (RA) discovered that 'Abdullah ibn 'Amr (RA) was ordering the women to undo their plaits of hair (for ghusl). She (RA) observed, "It is amazing that Ibn 'Amr (RA) orders the woment to undo the plaits of hair for ghusl. Why doesn't he just order them to shave their heads? I and the Messenger of Allah (Sallaho Alaihe Wassallam)  used to bathe from one vessel, and all I did was pour three handfuls of water over my head."[Ahmed, Muslim]

10. It is not necessary to do Wudhu afer Ghusl.

حدثنا إسماعيل بن موسى قال حدثنا شريك عن أبي إسحاق عن الأسود عن عائشة أن النبي صلى الله عليه وسلم كان لا يتوضأ بعد الغسل قال أبو عيسى هذا حديث حسن صحيح

Narrated Aisha, Ummul Mu'minin (RA) that the Apostle of Allah (Sallaho Alaihe Wassallam) did not perform Wudhu after taking a bath (Ghusl). [Abu Isa (Imam Tirmidhi) has declared this Hadeeth to be Hasan Sahih]

Compulsory actions of Ghusl (Faraidh):

1.     To gargle the mouth

2.     To clean the nostrils up to the soft part of the nose

3.     To pour water over the entire body

Sunnah actions of Ghusl:

1.     Make the intention for Ghusl, “I am performing Ghusl for Allah (SWT)”

2.     Recite بسم اللھ الرحمن الرحیم

3.     To wash hands up to the wrists

4.     To wash off all the impurities

5.     To wash the private parts even if there are no impurities on them

6.     Thereafter to perform Wudhu

7.     Thereafter to let water flow on the entire body three times

8.     When pouring water, start from the head, then the right and then the left side

9.     To rub the body

10.            Not to allow washed parts to get dry before making Ghusl