Johann, do you mean why the NT uses the word "grace," or why it discusses the concept of "grace," or both?
The word in English or Greek isn't used at all in Matthew or Mark, but it is used in every other NT book except 1 Jn. and 3 Jn.
What a shock! "Grace" is used in 74 verses in my English translation of the Koran. Add "gracious" and "graciously" and you end up with a total for the three words of 247 verses.
"Let them forgive and overlook. Do you not wish that Allah should forgive you?" 24:22.
That sounds good.
"And to preach thus, ‘Seek ye the forgiveness of your Lord, and turn to Him in repentance; that He may grant you enjoyment, good and true, for a term appointed, and bestow His abounding Grace on all who abound in merit!" 11:3.
That doesn't, since it sounds like it is saying that we can have merit ourselves.