Sahih Muslim Book 31, Hadith Number 5911.

Abu Musa Ash’ari reported that he performed ablution in his house and then came out saying: I would remain with Allah’s Messenger (may peace be upon him) the whole day long. He came to the mosque, and asked about Allah’s Apostle (may peace be upon him). They (his Companions) said: He has gone in this direction. He (Abu Musa Ash’ari) said: I followed his steps asking about him until I came to Bi’r Aris (it is a well in the suburb of Medina). I sat by its wooden door until Allah’s Messenger (may peace be upon him) had relieved himself and then performed ablution. I went to him and he was sitting with his shanks uncovered hp to the knees and his legs dangling in that well. I offered him salutations. I then came back and sat at the door as if I had been a chamberlain at the door of Allah’s Messenger (may peace be upon him) that day. There came Abu Bakr and knocked the door and I said: Who is it? He said: This is Abu Bakr. I said: Wait, please. I went and said: Allah’s Messenger, here is Abu Bakr seeking permission. Thereupon he said: Admit him and give him glad tidings of Paradise. I came and I said to Abu Bakr to get in (and also told him) that Allah’s Messenger (may peace be upon him) was giving him the glad tidings of Paradise. Abu Bakr got in and sat on the right side of Allah’s Messenger (may peace be upon him) and dangled his feet in the well as Allah’s Messenger (may peace be upon him) had done, and he uncovered his shanks. I then returned and sat there and I had left my brother as he had been performing ablution and he was to meet me and I said: If Allah would intend goodness for such and such he would intend goodness for his brother and He would bring him. I was thinking this that a person stirred the door. I said: Who is it. He said: This is Umar b., Khattab. I said: Wait. Then I came to Allah’s Messenger (may peace be upon him), greeted him and said: Here is ‘Umar seeking your permission to get in. Thereupon he said: Let him come in and give him glad tidings of Paradise. I came to Umar and said: There is permission for you and glad tidings for you from Allah’s Messenger (may peace be upon him) for Paradise. He got in and sat on the left side of Allah’s Messenger (may peace be upon him) with his feet dangling in the well. I then returned and sat and said: If Allah would intend goodness for such and such (that is for his brother), He would bring him. And I was contemplating over it that a man stirred the door and I said: Who is it? He said: This is Uthman b. Affan. I said: Wait, please. I then came to Allah’s Messenger (may peace be upon him) and informed him and he said: Admit him and give him glad tidings (and inform) him of the turmoil which he shall have to face. I came and said: Get in, Allah’s Messenger (may peace be upon him) gives you the glad tidings of Paradise along with the trial which you shall have to face. He got in and saw the elevated plan round the well fully occupied. He sat on the other side. Sharik said that Sa’id b. al-Musayyib reported: I drew a conclusion from it that their groves would be (in this very state, the graves of Hadrat Abu Bakr, ‘Umar Faruq by the tide of the Holy Prophet [may peace be upon him] and the grave of Hadrat ‘Uthman away from their graves).

Abu Musa. reported: I set out with the intention (of meeting) Allah’s Messenger (may peace be upon him) and came to know that he had gone to the gardens (in the suburb of Medina). I followed him and found him in a garden sitting upon an elevated place round the well with his shanks uncovered which had been dangling in the well. The rest of the hadith is the same but with this variation that there is no mention of the words of Sa’id: all drew a conclusion from it pertaining to their graves.”