Exasperated at the failure of their mission in Abyssinia, the Quraish stepped up their opposition to the Holy Prophet and his mission. The Holy Quran served as shield for the Muslims, and in order to break up this line of defense of the Muslims, the Quraish launched an attack against the Holy Quran. They levied the charge that the Holy Quran was not a revealed book, it owed its authorship to a Christian Jabir. Allah Himself refuted the charge by pointing out that Jabir was not Arab, and he was not proficient in the Arabic language. A challenge was given to the Quraish that if they maintained that the Quran was a work of human authorship, they should produce something like that. The Quraish were unable to accept the challenge and thus, attack on the Quran failed.
In the meantime, the Holy Quran showed its miraculous aspect in many ways, and came to the help of the Muslims when things had become difficult for them. One day, Umar a fiery youth among the Quraish and an inveterate enemy of the Muslims girded his sword and came out of his house with the intention of putting an end to the life of the Holy Prophet. In the way he met a friend who advised him to take care of his sister and her husband first who had become Muslims. At the house of his sister, Umar heard some verses of the Holy Quran, which moved him to such an extent that he hastened to the house of the Holy Prophet not with a view to killing him, but to owe him allegiance. The conversion of Umar to Islam proved to be a matter of great asset to the Muslims and a setback for the Quraish.
Al Tufail b Amr of the Daus tribe having heard of the Holy Prophet came to him at Makkah. Al Tufail was an eminent Arabic poet. The Quraish met Al Tufail, and put pressure on him not to see Muhammad (peace be on him) as he was a wizard and a sorcerer. Al Tufail said that he was a poet and after hearing the verses of the Holy Quran he would be in the position to judge how far the Quran was genuine or otherwise. He saw the Holy Prophet, heard some verses of the Holy Quran and was so much impressed that he lost no time in conversion to Islam.
A delegation of a dozen Christians from the interior of Arabia, having heard of the advent of the Holy Prophet, came to Makkah with a view to seeing the Holy Prophet. The Quraish tried to prevail upon them not to see the Holy Prophet as according to their assessment he was an imposter. The Christians said that they would be able to judge this issue for themselves after they had seen the Holy Prophet. They saw the Holy Prophet, heard the Holy Quran, were impressed and were converted to Islam.