Whenever the Messenger of Allah ﷺ came to someone's door, he would not stand directly facing it, but rather to its right corner or its left, and he would say, "Peace be upon you, peace be upon you." That was because in those days the houses had no curtains over their doors.
كان رسول الله ﷺ إذا أتى باب قوم لم يستقبل الباب من تلقاء وجهه، ولكن من ركنه الأيمن أو الأيسر، ويقول: السلام عليكم، السلام عليكم. وذلك أن الدور لم يكن عليها يومئذ ستور.
Reported by Abu Dawud (5186), Ahmad (17694), and Bukhari in Adab al-Mufrad (1078), all of them via Baqiya bin Walid, who said, our teacher told us, Muhammad bin Abdul-Rahman, from Abdullah bin Busr, who said, then he related it. Its chain is hasan because of Baqiya bin Walid, for his narration is hasan when he explicitly states that he heard it directly, and he did state this explicitly in this hadith, and it has also been corroborated. It was reported by Ahmad (17692) via Ismail bin Ayyash, and by Bayhaqi in Shuab al-Iman (8437) via Uthman bin Saeed bin Kathir, and also (8438) via Yahya bin Saeed the perfumer, all three of them narrating from Muhammad bin Abdul-Rahman with similar wording.