Musnad Ahmad 2963
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn ‘Abbas (رضي الله عنه) said: A group of the Companions of the Prophet (ﷺ) passed by a man of Banu Sulaim who had some sheep of his with him and he greeted them with salam. They said: He only greeted you with salam so as to protect himself from you. So they went to him and killed him, and they took his sheep and brought them to the Prophet (ﷺ). Then Allah, may He be blessed and exalted, revealed the words: "and say not to anyone who greets you (by embracing Islam): ‘You are not a believer’; seeking the perishable goods of the worldly life. There is much more profit and booty with Allah. Even as he is now, so were you yourselves before till Allah conferred on you His Favours (i.e. guided you to Islam), therefore, be cautious in discrimination. Allah is Ever Well-Aware of what you do." [an-Nisa' 4:94].