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

Bukhari :: Book 3 :: Volume 33 :: Hadith 255

Narrated 'Ali bin Al-Husain from Safiya:

Safiya went to the Prophet while he was in Itikaf. When she returned, the Prophet accompanied her walking. An Ansari man saw him. When the Prophet noticed him, he called him and said, "Come here. She is Safiya. (Sufyan a sub-narrator perhaps said that the Prophet had said, "This is Safiya"). And Satan circulates in the body of Adam's offspring as his blood circulates in it."

(A sub-narrator asked Sufyan, "Did Safiya visit him at night?" He said, "Of course, at night.")