The word(s) "forehead" appears 4 time(s) in 3 verse(s) in Quran in Mohsin Khan translation.

(1) On the Day when that (Al-Kanz: money, gold and silver the Zakat of which has not been paid) will be heated in the Fire of Hell and with it will be branded their foreheads, their flanks, and their backs, (and it will be said unto them): "This is the treasure which you hoarded for yourselves. Now taste of what you used to hoard."

(2) Then, when they had both submitted themselves (to the Will of Allah), and he had laid him prostrate on his forehead (or on the side of his forehead for slaughtering);

(3) Muhammad (صلى الله عليه وسلم) is the Messenger of Allah. And those who are with him are severe against disbelievers, and merciful among themselves. You see them bowing and falling down prostrate (in prayer), seeking Bounty from Allah and (His) Good Pleasure. The mark of them (i.e. of their Faith) is on their faces (foreheads) from the traces of prostration (during prayers). This is their description in the Taurat (Torah). But their description in the Injeel (Gospel) is like a (sown) seed which sends forth its shoot, then makes it strong, and becomes thick and it stands straight on its stem, delighting the sowers, that He may enrage the disbelievers with them. Allah has promised those among them who believe (i.e. all those who follow Islamic Monotheism, the religion of Prophet Muhammad صلى الله عليه وسلم till the Day of Resurrection) and do righteous good deeds, forgiveness and a mighty reward (i.e. Paradise).