Before the conquest of Mecca, Abu Sufiyan was the leader of the Quraish in Mecca. He was very hostile to Islam. He led the Quraish at the battle of Uhud. He was the leader of the Quraish at the battle of the Ditch. The Muslims suffered considerably at the hands of Abu Sufiyan. Umm Habiba a daughter of Abu Sufiyan, however, accepted Islam and was married to the Holy Prophet.
As Abu Sufiyan was the bitter enemy of Islam, Umar was very bitter against him. At the time of the conquest of Mecca when Abu Sufiyan came to the Muslim camp for negotiation, Umar sought the permission of the Holy Prophet to kill Abu Sufiyan. The Holy Prophet asked Umar to wait and watch further developments.
Thereafter Abu Sufiyan and all the Quraish of Mecca became Muslims. As Abu Sufiyan was an aristocrat, even after becoming a Muslim he could not get rid of his past arrogance.
In Madina a complaint was lodged before Umar against Abu Sufiyan. It was complained that Abu Sufiyan had constructed a house, and blocked the drainage so that the drainage water was diverted to the houses of neighbours thereby creating a nuisance and damaging such houses.
Umar decided that when he visited Mecca on the occasion of the Hajj he would see the site, and pass the necessary orders on the spot. When Umar came to Mecca he visited the site. It transpired that Abu Sufiyan had placed some stones in the drain in such a way that the flow of the sullage in the proper direction was obstructed and was instead diverted to the houses of the neighbours. Umar felt convinced that the conduct of Abu Sufiyan was not fair.
Umar summoned Abu Sufiyan and asked him to remove the stones so that the sullage should flow unobstructed. Abu Sufiyan contended that he had acted within right and as such was not going to comply with the orders of the Caliph. Umar flourished his whip and said, "Abu Sufiyan I command you to remove these stones forthwith, otherwise I will whip you, your status notwithstanding."
Without further contention, Abu Sufiyan removed the stones in the manner desired by Umar.
Thereupon turning his face to the Kaaba Urrar said:
"Praise be to God, Who, because of the power of Islam, made an ordinary man like Umar dominate over a chief like Abu Sufiyan."
Abu Sufiyan said:
"All praise is due to God Who blessed me with the light of Islam which has shown me the true path, and made me bow before the truth".
"Abu Sufiyan! Congratulations, for Islam has shown you the true path."