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." (TH)
English reference (TH): Vol. 1, Book 5, Hadith 922 (TH)
Arabic reference (TH): Book 5, Hadith 975 (TH)