Prior to the coming of Muhammad (PBUH) to Madina, the tribes of Aus and Khazraj were always quarreling with each other. They now felt that harmony and peaceful co-existence should be maintained between the people of Madina. They were keen to have a common ruler.
Abdullah bin Ubay bin Sulool, a citizen of Madina, was a very intelligent, experienced in worldly matters, clever and cunning person. He had great influence over the Aus and Khazraj tribes and the people of Madina accepted his leadership, and were prepared to crown him king and ruler of Madina.
He foresaw himself as a future king and ruler of Madina. After Muhammad (PBUH) and his followers entered Madina, they became a strong force and the people of Madina accepted the leadership of Muhammad (PBUH). This shattered the hopes of Abdullah bin Ubay bin Sulool of becoming the ruler of Madina.
Abdullah bin Ubay bin Sulool hoped that if Muhammad (PBUH) had not come to Madina he would have been installed as ruler of the city. Being a clever and cunning person, he hid his dislike and hatred for Muhammad (PBUH) and his followers accepted Islam to show everyone that they were Muslims but at heart they were dangerous enemies of Islam and they co-operated with the Jews in plotting against the Muslims.
The Jews found friends in these people as they had feared that they will lose control of the business of Madina. Abdullah bin Ubay bin Sulool and his followers are termed ‘MUNAFIQS’ (HYPOCRITES) in Islam.