Ibn Isḥāq said:
They returned to their people during the rest of Shawwāl or at the beginning of Dhū al-Qaʿdah. After their delegation had departed, the Messenger ﷺ sent ʿAmr ibn Ḥazm to them so that he might instruct them in the religion, teach them the Sunnah and the hallmarks of Islam, and collect their alms. He also wrote him a letter, entrusting him with the mission and detailing his instructions. Ibn Isḥāq reproduced this document, and we have already cited it—through the chain related by al-Bayhaqī—in the account of the delegation of the kings of Ḥimyar. Al-Nasāʾī likewise transmitted it, in wording similar to that cited by Muḥammad ibn Isḥāq, though without an isnād.
The Prophet’s dispatching of governors to the people of Yemen before the Farewell Pilgrimage to call them to Allah, Exalted is He
Al-Bukhārī said: “Chapter: The dispatch of Abū Mūsā and Muʿādh to Yemen before the Farewell Pilgrimage.”
Mūsā related to us; Abū ʿAwānah related to us; ʿAbd al-Malik related, from Abū Burdah, who said:
The Prophet ﷺ sent Abū Mūsā and Muʿādh ibn Jabal to Yemen, assigning each of them to a district. He said, “Yemen consists of two districts.” Then he instructed them:
“Make things easy and do not make them difficult; give glad tidings and do not drive people away.”
In another wording: “Work together and do not differ.”
Each of them set out to his appointed task. Whenever one of them travelled in his territory and came near his companion, he would visit him and convey greetings. Thus Muʿādh travelled through his area until he came close to Abū Mūsā. He approached on his mule until he reached him and found him seated with the people gathered around him, while a man stood nearby with his hands bound to his neck. Muʿādh said, “O ʿAbd Allah ibn Qays, who is this man?” He replied, “This is a man who reverted to unbelief after accepting Islam.” Muʿādh said, “I shall not dismount until he is executed.” Abū Mūsā answered, “He has been brought for that very purpose—so dismount.” Muʿādh repeated, “I will not dismount until he is killed.” The order was therefore given and the man was executed; only then did Muʿādh dismount.