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

(51) "And my brother Harun (Aaron) - he is more eloquent in speech than me: so send him with me as a helper to confirm me. Verily I fear that they will belie me."

(52) He has created the heavens without any pillars that you see, and has set on the earth firm mountains lest it should shake with you. And He has scattered therein moving (living) creatures of all kinds. And We send down water (rain) from the sky, and We cause (plants) of every goodly kind to grow therein.

(53) And what We have revealed to you (O Muhammad صلى الله عليه وسلم), of the Book (the Qur'an), it is the (very) truth [that you (Muhammad صلى الله عليه وسلم) and your followers must act on its instructions], confirming that which was (revealed) before it. Verily! Allah is indeed All-Aware, and All-Seer of His slaves.

(54) Nay! he (Muhammad صلى الله عليه وسلم) has come with the truth (i.e. Allah's religion - Islamic Monotheism and this Qur'an) and he confirms the Messengers (before him who brought Allah's religion - Islamic Monotheism).

(55) He placed therein (i.e. the earth) firm mountains from above it, and He blessed it, and measured therein its sustenance (for its dwellers) in four Days equal (i.e. all these four days were equal in the length of time) for all those who ask (about its creation).

(56) Verily, those who say: "Our Lord is Allah (Alone)," and then they stand firm, on them the angels will descend (at the time of their death) (saying): "Fear not, nor grieve! But receive the glad tidings of Paradise which you have been promised!

(57) And who is better in speech than he who [says: "My Lord is Allah (believes in His Oneness)," and then stands firm (acts upon His Order), and] invites (men) to Allah's (Islamic Monotheism), and does righteous deeds, and says: "I am one of the Muslims."

(58) So unto this (religion of Islam alone and this Qur'an) then invite (people) (O Muhammad صلى الله عليه و سلم), and stand firm [on Islamic Monotheism by performing all that is ordained by Allah (good deeds), and by abstaining from all that is forbidden by Allah (sins and evil deeds)], as you are commanded, and follow not their desires but say: "I believe in whatsoever Allah has sent down of the Book [all the holy Books, - this Qur'an and the Books of the old from the Taurat (Torah), or the Injeel (Gospel) or the Pages of Ibrahim (Abraham)] and I am commanded to do justice among you. Allah is our Lord and your Lord. For us our deeds and for you your deeds. There is no dispute between us and you. Allah will assemble us (all), and to Him is the final return."

(59) And when it was said: "Verily, Allah's Promise is the truth, and there is no doubt about the coming of the Hour," you said: "We know not what is the Hour: we do not think it but as a conjecture, and we have no firm convincing belief (therein)."

(60) And before this was the Scripture of Musa (Moses) as a guide and a mercy. And this is a confirming Book (the Qur'an) in the Arabic language, to warn those who do wrong, and as glad tidings to the Muhsinun (good-doers. See the footnote of V.9:120).