Silsilat al-Ahadith al-Sahihah

Aswad bin Yazid says: The iqamah was called for prayer in the mosque, and we set out towards the mosque with Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him). The people were in the state of bowing (ruku‘), so Sayyiduna Abdullah performed ruku‘ (before reaching the row), and we also bent for ruku‘ and, while in the state of ruku‘, walked and stood in the row. A man passed in front of Sayyiduna Abdullah and said: Abu Abdur-Rahman! As-salamu ‘alaykum. Sayyiduna Abdullah, while in the state of ruku‘, said: Allah and His Messenger (ﷺ) have spoken the truth. When they finished the prayer, some people asked: When that man greeted you with salam, why did you say: Allah and His Messenger have spoken the truth? He replied: I heard the Messenger of Allah (ﷺ) say: “This too is among the signs of the Hour, that salam will be given only on the basis of acquaintance.” And in another narration: “A man will greet another with salam, but will do so only on the basis of acquaintance.”