Hadith 517452
Chapter 53: Greetings - كتاب السلام
وَحَدَّثَنِي عَنْ مَالِكٍ أَنَّهُ بَلَغَهُ إِذَا دُخِلَ الْبَيْتُ غَيْرُ الْمَسْكُونِ يُقَالُ السَّلاَمُ عَلَيْنَا وَعَلَى عِبَادِ اللَّهِ الصَّالِحِينَ .
Yahya related to me from Malik that he heard that when one entered an unoccupied house, one should say, "Peace be upon us and on the slaves of Allah, who are salih." (As-salamu alayna wa ala ibadillahi's-saliheen).O
Reference Muwatta Malik 517452
USC-MSA web (English) reference : Book 53, Hadith 8