The word(s) "letter" appears 6 time(s) in 6 verse(s) in Quran in Saheeh International translation.

(1) And among them are unlettered ones who do not know the Scripture except in wishful thinking, but they are only assuming.

(2) Those who follow the Messenger, the unlettered prophet, whom they find written in what they have of the Torah and the Gospel, who enjoins upon them what is right and forbids them what is wrong and makes lawful for them the good things and prohibits for them the evil and relieves them of their burden and the shackles which were upon them. So they who have believed in him, honored him, supported him and followed the light which was sent down with him - it is those who will be the successful.

(3) Say, [O Muhammad], "O mankind, indeed I am the Messenger of Allah to you all, [from Him] to whom belongs the dominion of the heavens and the earth. There is no deity except Him; He gives life and causes death." So believe in Allah and His Messenger, the unlettered prophet, who believes in Allah and His words, and follow him that you may be guided.

(4) Take this letter of mine and deliver it to them. Then leave them and see what [answer] they will return."

(5) She said, "O eminent ones, indeed, to me has been delivered a noble letter.

(6) It is He who has sent among the unlettered a Messenger from themselves reciting to them His verses and purifying them and teaching them the Book and wisdom - although they were before in clear error -