‘Ali b. Talq reported God’s messenger as saying, “When any of you breaks wind he should perform ablution, and you must not have intercourse with women by their buttocks.”
He also reported God's messenger as saying, “The key of prayer is purification, saying ‘God is most great’ makes it a sacred state, and the salutation brings the sacred state to an end.”
Abu Dawud, Tirmidhi and Darimi transmitted it, and Ibn Majah transmitted it both from 'Ali and from Abu Sa'id.
Mu'awiya b. Abu Sufyan reported the Prophet as saying, “The eyes are the leather strap of the anus, and when the eye sleeps the leather strap is loosened.”