It wasnarrated that Samurah bin Jundab said:
"The Messenger of Allah(ﷺ) commanded us to greet our Imam with Salam, and to greet oneanother with Salam." (TR)
English reference (TR): Vol. 1, Book 5, Hadith 922 (TR)
Arabic reference (TR): Book 5, Hadith 975 (TR)