The word(s) "firm" appears 66 time(s) in 64 verse(s) in Quran in Saheeh International translation.

(1) And believe in what I have sent down confirming that which is [already] with you, and be not the first to disbelieve in it. And do not exchange My signs for a small price, and fear [only] Me.

(2) And when there came to them a Book from Allah confirming that which was with them - although before they used to pray for victory against those who disbelieved - but [then] when there came to them that which they recognized, they disbelieved in it; so the curse of Allah will be upon the disbelievers.

(3) And when it is said to them, "Believe in what Allah has revealed," they say, "We believe [only] in what was revealed to us." And they disbelieve in what came after it, while it is the truth confirming that which is with them. Say, "Then why did you kill the prophets of Allah before, if you are [indeed] believers?"

(4) Say, "Whoever is an enemy to Gabriel - it is [none but] he who has brought the Qur'an down upon your heart, [O Muhammad], by permission of Allah, confirming that which was before it and as guidance and good tidings for the believers."

(5) And when a messenger from Allah came to them confirming that which was with them, a party of those who had been given the Scripture threw the Scripture of Allah behind their backs as if they did not know [what it contained].

(6) And when they went forth to [face] Goliath and his soldiers, they said, "Our Lord, pour upon us patience and plant firmly our feet and give us victory over the disbelieving people."

(7) He has sent down upon you, [O Muhammad], the Book in truth, confirming what was before it. And He revealed the Torah and the Gospel.

(8) It is He who has sent down to you, [O Muhammad], the Book; in it are verses [that are] precise - they are the foundation of the Book - and others unspecific. As for those in whose hearts is deviation [from truth], they will follow that of it which is unspecific, seeking discord and seeking an interpretation [suitable to them]. And no one knows its [true] interpretation except Allah. But those firm in knowledge say, "We believe in it. All [of it] is from our Lord." And no one will be reminded except those of understanding.

(9) So the angels called him while he was standing in prayer in the chamber, "Indeed, Allah gives you good tidings of John, confirming a word from Allah and [who will be] honorable, abstaining [from women], and a prophet from among the righteous."

(10) And [I have come] confirming what was before me of the Torah and to make lawful for you some of what was forbidden to you. And I have come to you with a sign from your Lord, so fear Allah and obey me.