Retiring to a Mosque for Remembrance of Allah (I'tikaf)

Bukhari :: Book 3 :: Volume 33 :: Hadith 256

Narrated Abu Said:

We practiced Itikaf with Allah's Apostle in the middle ten days (of Ramadan). In the morning of the twentieth (of Ramadan) we shifted our baggage, but Allah's Apostle came to us and said, "Whoever was m Itikaf should return to his place of Itikaf, for I saw (i.e. was informed about the date of) this Night (of Qadr) and saw myself prostrating in mud and water." When I returned to my place the sky was overcast with clouds and it rained. By Him Who sent Muhammad with the Truth, the sky was covered with clouds from the end of that day, and the mosque which was roofed with leaf-stalks of date palm trees (leaked with rain) and I saw the trace of mud and water over the nose of the Prophet and its tip.