عَلَىٰ قَلْبِكَ لِتَكُونَ مِنَ ٱلْمُنذِرِينَ
Commentary:
The words 'on thy heart' have been added to indicate that the Quranic revelations were not merely inspired ideas which the Holy Prophet expressed in his own words but were the actual words of God Himself which descended upon the Prophet’s heart through the medium of Gabriel. The verse also implies reference to a famous prophecy of Moses (Deut. 18:18) in which it is stated that God would put His words in the mouth of the Prophet whom He would raise from among the brethren of the Israelites. Of all revealed scriptures, the Quran stands unique in this respect that from beginning to end it is the spoken Word of God (کلام اللّٰه).
The allusion in the words "on thy heart" may also be to the purity of the Holy Prophet’s heart and his perfect aptitude for receiving Divine revelation to which a beautiful reference has also been made in 24:36.
It may be noted in passing that Divine revelation descends, besides the heart, on the tongue and the ears. In 75:17 we have the words, "move not thy tongue with this revelation that thou mayest hasten to preserve it," which shows that revelation descends on the tongue also. The Holy Prophet is reported to have said: "Sometimes the angel takes the form of a man and talks to me and I remember what he says" (Bukhari). This hadith shows that revelation descends on the ears also. But the revelation which descends upon the tongue or the ear descends at the same time on the heart as well.
The words 'on thy heart' have been added to indicate that the Quranic revelations were not merely inspired ideas which the Holy Prophet expressed in his own words but were the actual words of God Himself which descended upon the Prophet’s heart through the medium of Gabriel.