The Prophet (s) met six members of Khazraj from Medina 11 years after Bi'that/619. He introduced Islam and Qur'an to them. People of Medina vaguely knew about a prophet in Mecca, and they hoped the Prophet (s) could stop the adversaries between the tribes of Aws and Khazraj. After they returned to Medina, they told about the Prophet to people.
In the first Pledge of al-'Aqaba, also known as "Bay'at al-Nisa'", twelve members of Aws and Khazraj converted to Islam and took an oath of allegiance to Prophet Muhammad (s) in the time of Hajj, twelve years after Bi'that/621.
After the first Pledge of al-'Aqaba, Prophet Muhammad (s) sent Mus'ab b. 'Umayr to Medina to teach Qur'an to newly converted Muslims.
The second Pledge of al-'Aqaba, also known as "Bay'at al-Harb" (Pledge of War), took place near Mina, Mecca in the time of Hajj, thirteen years after Bi'that/622.
The significance of these pledges of allegiance is that both were important in preparation of situation for migration of Prophet Muhammad (s) and Muslims from Mecca to Medina. Read more...