Sayyiduna Aswad bin Yazid (may Allah be pleased with him) narrates that the prayer had already started in the mosque and we were coming along with Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him). When the people bowed (in ruku'), Sayyiduna Abdullah (may Allah be pleased with him) also bowed and we bowed along with him, even though we were still walking. Meanwhile, a man passed by and said: O Abu Abdur Rahman! As-salamu 'alaykum. Hearing this, Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said in the state of ruku': "Sadaq Allahu wa Rasuluhu" (Allah and His Messenger have spoken the truth). When he finished the prayer, some people asked: When a man greeted you with salam, why did you say that Allah and His Messenger have spoken the truth? He replied: I heard the Noble Prophet (peace and blessings be upon him) say that among the signs of the Hour is that salam will be given only on the basis of acquaintance.