General Behavior (Kitab Al-Adab)
Dawud :: Book 41 : Hadith 5167
Narrated Abdullah ibn Busr:
When the Apostle of Allah (peace_be_upon_him) came to some people's door, he did not face it squarely, but faced the right or left corner, and said: Peace be upon you! peace be upon you! That was because there were no curtains on the doors of the house at that time.