The word(s) "once" appears 105 time(s) in 102 verse(s) in Quran in Mohsin Khan translation.

(1) And if you (Arab pagans, Jews, and Christians) are in doubt concerning that which We have sent down (i.e. the Qur'an) to Our slave (Muhammad صلى الله عليه وسلم), then produce a Surah (chapter) of the like thereof and call your witnesses (supporters and helpers) besides Allah, if you are truthful.

(2) He said: "O Adam! Inform them of their names," and when he had informed them of their names, He said: "Did I not tell you that I know the Ghaib (Unseen) in the heavens and the earth, and I know what you reveal and what you have been concealing?"

(3) And mix not truth with falsehood, nor conceal the truth [i.e. Muhammad صلى الله عليه وسلم is Allah's Messenger and his qualities are written in your Scriptures, the Taurat (Torah) and the Injeel (Gospel)] while you know (the truth).

(4) Know they (Jews) not that Allah knows what they conceal and what they reveal?

(5) Or say you that Ibrahim (Abraham), Isma'il (Ishmael), Ishaq (Isaac), Ya'qub (Jacob) and Al-Asbat [the offspring of the twelve sons of Ya'qub (Jacob)] were Jews or Christians? Say, "Do you know better or does Allah (knows better ... that they all were Muslims)? And who is more unjust than he who conceals the testimony [i.e. to believe in Prophet Muhammad صلى الله عليه وسلم when he comes, as is written in their Books. (See Verse 7:157)] he has from Allah? And Allah is not unaware of what you do."

(6) Those to whom We gave the Scripture (Jews and Christians) recognise him (Muhammad صلى الله عليه وسلم or the Ka'bah at Makkah) as they recognise their sons. But verily, a party of them conceal the truth while they know it - [i.e. the qualities of Muhammad صلى الله عليه وسلم which are written in the Taurat (Torah) and the Injeel (Gospel)].

(7) Verily, those who conceal the clear proofs, evidence and the guidance, which We have sent down, after We have made it clear for the people in the Book, they are the ones cursed by Allah and cursed by the cursers.

(8) Except those who repent and do righteous deeds, and openly declare (the truth which they concealed). These, I will accept their repentance. And I am the One Who accepts repentance, the Most Merciful.

(9) Verily, those who conceal what Allah has sent down of the Book, and purchase a small gain therewith (of worldly things), they eat into their bellies nothing but fire. Allah will not speak to them on the Day of Resurrection, nor purify them, and theirs will be a painful torment.

(10) But he who fears from a testator some unjust act or wrong-doing, and thereupon he makes peace between the parties concerned, there shall be no sin on him. Certainly, Allah is Oft-Forgiving, Most Merciful.