The hadeeth refers to when a person is praying in congregation. When a person concludes his prayer, when he says assalamu alaikum wa rahmatullah, he is giving salam and responding to it from and to his brothers next to them.

What does “brothers” refer to in this hadith:”It is enough for each of you to place his hand on his thigh, and then salute his brothers who are on his right and left.”(Muslim, Ibn Khuzaimah & Tabaraani)