It is narrated from Sayyiduna Mu'adh that the Prophet (peace and blessings be upon him) said: Whoever comes to a gathering of people, it is his right to greet the people with salam. Similarly, whoever gets up to leave a gathering, it is also his right to leave after giving salam. While the Prophet (peace and blessings be upon him) was still speaking, a man got up and left without giving salam. The Prophet (peace and blessings be upon him) said: How quickly he forgot.