Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) narrates that the obligation of prayer was established in three stages, and the obligation of fasting was also established in three stages. The stages of prayer are as follows: When the Noble Prophet (peace and blessings be upon him) migrated to Madinah Munawwarah, he (peace and blessings be upon him) prayed facing the Ka'bah for seventeen months, ... ... (The complete hadith has already been mentioned in the Book of Prayer.) The stages of fasting are as follows: When the Messenger of Allah (peace and blessings be upon him) migrated to Madinah Munawwarah, he (peace and blessings be upon him) used to fast three days every month. Yazid, the narrator, says: From Rabi' al-Awwal until the obligation of fasting in the month of Ramadan, during a total of seventeen months, he (peace and blessings be upon him) used to fast three days every month. He (peace and blessings be upon him) also fasted on the tenth of Muharram. Then Allah Almighty made the fasting of the month of Ramadan obligatory upon him (peace and blessings be upon him) and revealed these verses: {یَا اَیُّہَا الَّذِیْنَآمَنُوا کُتِبَ عَلَیْکُمُ الصِّیَامُ کَمَا کُتِبَ عَلَی الَّذِیْنَ مِنْ قَبْلِکُمْ لَعَلَّکُمْ تَتَّقُوْنَ۔} (O you who believe! Fasting is prescribed for you as it was prescribed for those before you, so that you may become righteous.) And He said: { وَعَلَی الَّذِیْنَیُطِیْقُوْنَہُ فِدْیَۃٌ طَعَامُ مِسْکِیْنٍ} (And those who are able to fast but with hardship, they can substitute by feeding a poor person [for each day] .) Acting upon these verses, whoever wished would fast, and whoever did not wish to fast would feed a poor person as compensation, and that would suffice for him. After that, Allah Almighty revealed this command: {شَہْرُ رَمَضَانَ الَّذِی اُنْزِلَ فیِہِ الْقُرْآنُ ھُدًی لِّلنَّاسِ وَبَیِّنَاتٍ مِّنَ الْھُدٰی وَالْفُرْقَانِ فَمَنْ شَہِدَ مِنْکُمُ الشَّہْرَ فَلْیَصُمْہُ} (The month of Ramadan is that in which was revealed the Qur'an, a guidance for the people and clear proofs of guidance and criterion. So whoever sights [the new moon of] the month, let him fast it.) In this way, Allah Almighty made fasting in this month obligatory upon every resident and healthy person, but gave concession to the sick and the traveler to not fast, and for the elderly who could not bear to fast, the ruling remained that they should feed a poor person as compensation. These are two conditions. The third condition was that people could eat, drink, and have relations with their wives until they slept at night, but once they slept, all of this became forbidden for them. One day, it happened that an Ansari companion named Surmah worked all day while fasting. When evening came, he reached home, prayed the 'Isha prayer, and slept without eating or drinking, until morning came and thus his fast had already begun. When the Messenger of Allah (peace and blessings be upon him) saw him and noticed that he was very exhausted, he (peace and blessings be upon him) asked him: "You look very exhausted, what is the reason?" He said: "O Messenger of Allah! I worked all day yesterday, and when I came home and lay down, I fell asleep (and thus eating and drinking became forbidden for me), and when morning came, I had to remain fasting." Meanwhile, Sayyiduna 'Umar bin Khattab (may Allah be pleased with him) also had an incident where, after waking up from sleep, he had relations with his wife or slave woman, and he came to the Messenger of Allah (peace and blessings be upon him) and told him the whole matter. At that time, Allah Almighty revealed this command: {اُحِلَّ لَکُمْ لَیْلَۃَ الصِّیَامِ الرَّفَثُ … … ثُمَّ اَتِمُّوْا الصِّیامَ إِلَی الَّیْلِ۔} (It has been made permissible for you the night preceding fasting to go to your wives [for sexual relations] . They are clothing for you and you are clothing for them. Allah knows that you used to deceive yourselves, so He accepted your repentance and forgave you. So now, have relations with them and seek that which Allah has decreed for you. And eat and drink until the white thread of dawn becomes distinct to you from the black thread [of night] . Then complete the fast until the night.)

Nadr bin Shaiban says: I met Abu Salamah bin Abdur Rahman and said to him: Tell me a hadith about the month of Ramadan which you heard from your father and he heard from the Messenger of Allah, peace and blessings be upon him. He said: Yes, my father, Sayyiduna Abdur Rahman bin Awf, may Allah be pleased with him, narrated to me that he heard the Messenger of Allah, peace and blessings be upon him, say: Allah Almighty has made the fasting of the month of Ramadan obligatory, and I have declared standing (in prayer) during Ramadan as Sunnah. Whoever fasts during this month and stands (in prayer) seeking reward, he will be cleansed of his sins as if his mother gave birth to him today.

It is narrated from Sayyiduna Abu Dharr (may Allah be pleased with him) that he said: O Messenger of Allah! What is fasting? The Prophet (peace and blessings be upon him) said: It is a debt, which will be repaid.