Majma al-Zawaid — Hadith 11277

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: When this verse was revealed: "O Prophet! Indeed, We have sent you as a witness, a bearer of glad tidings and a warner", the Prophet (peace and blessings be upon him) called Sayyiduna Ali (may Allah be pleased with him) and Sayyiduna Mu'adh (may Allah be pleased with him); he had ordered both of them to go to Yemen. Then he said: "Set out, both of you! Give glad tidings and do not drive people away; make things easy and do not make them difficult, for this verse has been revealed to me: 'O Prophet! Indeed, We have sent you as a witness' - that is, you are a witness over your Ummah - 'a bearer of glad tidings' - that is, of Paradise - 'and a warner' - that is, against Hellfire - 'and a caller to Allah Almighty' - that is, a caller to bearing witness that there is no god but Allah Almighty - 'by His permission, and (sent you) as a shining lamp' - here 'by His permission' refers to by the Qur'an."
Al-Tabarani recorded it; its chain contains a narrator, Abd al-Rahman bin Muhammad bin Abdullah al-Arzami, who is da'if (weak).