Hadith 17:393
Mu'adh ibn Mu'adh and Abu Usamah narrated to us, from Ibn 'Awn, who said: When it was said to Muhammad, "So-and-so sends you greetings of peace," he would say, "Upon you and upon him be peace."
حدثنا معاذ بن معاذ وأبو أسامة عن بن عون قال كان محمد إذا قيل له أن فلانا يقرئك السلام قال وعليك وعليه السلام