Musannaf Ibn Abi Shayba 27:880

Ahmad ibn al-Mufaddal narrated to us, he said: Asbat ibn Nasr narrated to us, from al-Suddi, from Abu Sa’id al-Azdi, from Abu al-Kunud, from Khabbab ibn al-Aratt regarding [the verse]: "And do not drive away those who call upon their Lord morning and evening, seeking His countenance." He said: Al-Aqra’ ibn Habis al-Tamimi and Uyaynah ibn Hisn al-Fazari came and found him [the Prophet] sitting with Bilal, Ammar, Suhayb, and Khabbab ibn al-Aratt among a group of the weak ones of the believers. When they saw them around him, they belittled them. They came to him and took him aside and said: "We would like for you to assign us a place from you by which the Arabs may recognize our status, for the delegations of the Arabs come to you, and we are ashamed that they see us with these slaves. So when we come to you, send them away from us, and when we are finished, sit with them if you wish." He said: "Yes." They said: "Then write a document for us." He called for a parchment to be written upon, and he called Ali to write. When he intended to do that, and we were sitting to the side, Gabriel descended upon him and said: "And do not drive away those who call upon their Lord morning and evening, seeking His countenance," up to His saying: "...then you would drive them away and be among the wrongdoers."