The word(s) "firm" appears 74 time(s) in 72 verse(s) in Quran in Mohsin Khan translation.

(21) And in their footsteps, We sent 'Îsa (Jesus), son of Maryam (Mary), confirming the Taurat (Torah) that had come before him, and We gave him the Injeel (Gospel), in which was guidance and light and confirmation of the Taurat (Torah) that had come before it, a guidance and an admonition for Al-Muttaqun (the pious - See V.2:2).

(22) And We have sent down to you (O Muhammad صلى الله عليه وسلم) the Book (this Qur'an) in truth, confirming the Scripture that came before it and Muhaymin (trustworthy in highness and a witness) over it (old Scriptures) . So judge among them by what Allah has revealed, and follow not their vain desires, diverging away from the truth that has come to you. To each among you, We have prescribed a law and a clear way. If Allah had willed, He would have made you one nation, but that (He) may test you in what He has given you; so compete in good deeds. The return of you (all) is to Allah; then He will inform you about that in which you used to differ.

(23) Do they then seek the judgement of (the days of) Ignorance? And who is better in judgement than Allah for a people who have firm Faith.

(24) If then it gets known that these two had been guilty of sin, let two others stand forth in their places, nearest in kin from among those who claim a lawful right. Let them swear by Allah (saying): "We affirm that our testimony is truer than that of both of them, and that we have not trespassed (the truth), for then indeed we should be of the wrong-doers."

(25) And this (the Qur'an) is a blessed Book which We have sent down, confirming (the revelations) which came before it, so that you may warn the Mother of Towns (i.e. Makkah) and all those around it. Those who believe in the Hereafter believe in it (the Qur'an), and they are constant in guarding their Salat (prayers).

(26) Thus truth was confirmed, and all that they did was made of no effect.

(27) And We wrote for him on the Tablets the lesson to be drawn from all things and the explanation for all things (and said): Hold unto these with firmness, and enjoin your people to take the better therein. I shall show you the home of Al-Fasiqun (the rebellious, disobedient to Allah).

(28) And (remember) when We raised the mountain over them as if it had been a canopy, and they thought that it was going to fall on them. (We said): "Hold firmly to what We have given you [i.e. the Taurat (Torah)], and remember that which is therein (act on its commandments), so that you may fear Allah and obey Him."

(29) (Remember) when He covered you with a slumber as a security from Him, and He caused water (rain) to descend on you from the sky, to clean you thereby and to remove from you the Rijz (whispering, evil-suggestions) of Shaitan (Satan), and to strengthen your hearts, and make your feet firm thereby.

(30) (Remember) when your Lord revealed to the angels, "Verily, I am with you, so keep firm those who have believed. I will cast terror into the hearts of those who have disbelieved, so strike them over the necks, and smite over all their fingers and toes."