The group then returned to Medinah, so the Prophet (peace be upon him) sent Mus’ab ibn Umair (may Allah be pleased with him) with them. Consequently, he was the first ambassador in Islam. The Prophet (peace be upon him) ordered him to recite Quran to them, teach them Islam, and explain Allah’s religion to them.
Mus’ab was known in Medinah as a reciter. He stayed with Asad ibn Zurarah, and he used to lead the people in prayer, as Al-Aws and Al-Khazraj did not like that one from the other tribe would lead them in prayer [adapted from The Prophet’s Biography by Ibn Hesham].
Many of Al-Ansar embraced Islam due to him. Before the Hajj season in the thirteenth year of the call, Mus’ab ibn Umair returned to Mecca to tell the Prophet (peace be upon him) what had happened with regards to the success and help from Allah in his task [adapted from The Blessed Garden].
This victory was the result of the fruits of eleven years of effort, exertion and patient perseverance, until the way out of difficulties eventually came. Allah (Glorified is He) could have easily formed an Islamic society without this exertion, but this is the way of Allah (sunnah) with His slaves.
It is possible to notice that the conditions of the first pledge did not entail only the first two testimonies of faith, but also ways and dealings of the individuals with each other. This is one of the aims of worship, and one of the reasons one performs worship.
This clarifies that the responsibility of the call is not limited to only the Prophets and Messengers, but it is the responsibility of every muslim. One example which illustrated this is the mission of Mus’ab ibn Umair, although the Prophet (peace be upon him) was alive at that time [adapted from The Sealed Nectar].