Sahih Bukhari, Chapter: Minor Pilgrimage (Umra)

I heard Al-Bara saying, "The above Verse was revealed regarding us, for the Ansar on returning from Hajj never entered their houses through the proper doors but from behind. One of the Ansar came and entered through the door and he was taunted for it. Therefore, the following was revealed: "It is not righteousness That you enter the houses from the back, But the righteous man is He who fears Allah, Obeys His order and keeps away from What He has forbidden So, enter houses through the proper doors." (2.189)