After the Pledge (in the form of an oath had been taken) the Prophet (Peace be upon him) sent to Yathrib (Madinah) Mus‘ab bin ‘Umair Al-‘Abdari, (May Allah be pleased with him) the first Muslim ‘ambassador’ to teach the people there the doctrines of Islam, give them practical guidance and make attempts at propagating the Islam among those who still professed polytheism. As‘ad bin Zurarah hosted him in Madinah. So prepared was the ground, and so zealous the propagation that the Islam spread rapidly from house to house and from tribe to tribe. There were various cheerful and promising aspects of success that characterized Mus‘ab’s task. One day Mus‘ab and As‘ad were on their way to the habitations of Bani ‘Abd Al-Ashhal and Bani Zafar, when they went into the premises of the latter clan. There they sat near a well conversing with some new converts. Sa‘d bin Mu‘adh and Usaid bin Hudair, chiefs of the two clans heard of this meeting, so Usaid approached the Muslims armed with his lance while the other Sa‘d excused himself on grounds that As‘ad was his maternal cousin. Usaid came closer cursing and swearing and accused the two men of befooling people weak of heart, and ordered that they stop it altogether. Mus‘ab calmly invited him to sit saying, “If you are pleased with our talk, you can accept it; should you hold it in abhorrence, you could freely immunize yourself against what you hate.” “That’s fair,” said Usaid, pierced his lance in the sand, listened to Mus‘ab and then heard some verses of the Noble Qur’ân. His face bespoke satisfaction and pleasure before uttering any words of approval. He asked the two men about the procedures pertinent to embracing Islam. They asked him to observe washing, purge his garment, bear witness to the Truth and then perform two Rak‘a. He responded and did exactly what he was asked to do, and then said there was a man (Sa‘d bin Mu‘adh) whose people would never hang back if he followed the Islam. He then left to see Sa‘d and his people. Sa‘d could immediately understand that Usaid had changed. To a question posed by Sa‘d, Usaid said that two men were ready to comply with whatever orders they received. He then managed a certain situation that provided the two men with a chance to talk with Sa‘d privately. The previous scene with Usaid recurred and Sa‘d embraced Islam, and directly turned to his people swearing that he would never talk with them until they had believed in Allâh, and in His Messenger. Hardly did the evening of that day arrive when all the men and women of that sept of Arabians embraced Islam with the exception of one, Al-Usairim, who hung back until the Day of Uhud. On that day he embraced Islam and fought the polytheists but was eventually killed before observing any prostration in the way of prayer. The Prophet (Peace be upon him) commented saying: “He has done a little but his reward is great.”
Mus‘ab stayed in Madinah carrying out his mission diligently and successfully until all the houses of Al-Ansar (the future Helpers) had Muslims elements, men and women. One family only stood obdurate to the Islamic Da‘wah (Call). They were under the influence of the poet Qais bin Al-Aslat, who managed to hold them at bay and screen off the Call of Islam from their ears until the year 5 A.H.
Shortly before the approach of the following pilgrimage season, i.e. the thirteenth year of Prophethood, Mus‘ab bin ‘Umair returned to Makkah carrying to the Prophet (Peace be upon him) glad tidings about the new fertile soil ofIslam in Madinah, and its environment rich in the prospects of good, and the power and immunity that that city was bound to provide to the cause of Islam.