The Ruling on Greeting Among Muslims

Question:
Peace be upon you. The prayer. Peace, peace.

Answer:
Congregational prayer is a collective obligation (fard kifayah), but if there is only one person, no. One begins with the greeting, and then the response is obligatory. When meeting, the better of the two is the one who initiates the greeting. The one who initiates is better, and the one who is greeted must respond; he must respond. Even if it were said to be obligatory, there is evidence for it; because the Messenger (peace and blessings be upon him) said , so the apparent meaning of the command is obligation. It is incumbent upon the believer when he meets his brother to strive to initiate the greeting so that he may attain the reward.