Translation of the verse 2 from Surah Al-Qalam : Number of verses 52 - - page 564 - Part 29.
You (O Muhammad SAW) are not, by the Grace of your Lord, a madman.
You are not, [O Muhammad], by the favor of your Lord, a madman.
(68:2) By your Lord's Grace, you are not afflicted with madness, *2
*2) That is for which an oath has been sworn by the Pen and by the Book. It means that this Qur'an which is being inscribed by the hands of the writers of Revelation, is by itself enough to refute the slander of the disbelievers who say that the Holy Prophet (upon whom be peace) is, God forbid, a madman, Before his claim to the Prophethood, the people of Makkah looked upon him as the best of their men and trusted his honesty, intelligence and sagacity. But when he started reciting the Qur'an before them they began to call him a madman. This meant that the Qur'an itself in their sight was the cause because of which they accused him of madness; Therefore, it was said: "The Qur'an by itself is a sufficient proof for the refutation of this slander. The presentation of this highly eloquent Revelation which consists of sublime themes, is an argument which proves that Muhammad (upon whom be Allah's peace and blessings) has been especially favoured by Allah, and nor an argument which might be used to prove that he has, God forbid, gone mad." Here, one should remember that although the address apparently is directed to the Holy Prophet, yet the real object is to nail the calumny of the disbelievers. Therefore, no ane should have the doubt that this verse was sent down only to assure the Holy Prophet that he was not mad. Obviously, the Holy Prophet himself had no such doubt for removing which he might have stood in need of such an assurance. The object was to tell the disbelievers, as if to say: "The Qur'an because of which you-are calling the one presenting it a madman, is by itself an argument that your accusation is false." (For further explanation' see E.N. 22 of Surah At-Tur)
Source : Al-Qalam Verse 2: You are not, [O Muhammad], by the favor of your Lord, a madman.