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

(41) Verily, those who divide their religion and break up into sects (all kinds of religious sects) , you (O Muhammad صلى الله عليه وسلم) have no concern in them in the least. Their affair is only with Allah, Who then will tell them what they used to do.

(42) "Proper it is for me that I say nothing concerning Allah but the truth. Indeed I have come unto you from your Lord with a clear proof. So let the Children of Israel depart along with me."

(43) Disputing with you concerning the truth after it was made manifest, as if they were being driven to death, while they were looking (at it).

(44) Should they find a refuge, or caves, or a place of concealment, they would turn straightway thereto with a swift rush.

(45) They (the hypocrites) will present their excuses to you (Muslims), when you return to them. Say (O Muhammad صلى الله عليه وسلم) "Present no excuses, we shall not believe you. Allah has already informed us of the news concerning you. Allah and His Messenger will observe your deeds. In the end you will be brought back to the All-Knower of the unseen and the seen, then He (Allah) will inform you of what you used to do." [Tafsir At-Tabari]

(46) See they not that they are put in trial once or twice every year (with different kinds of calamities, disease, famine)? Yet, they turn not in repentance, nor do they learn a lesson (from it).

(47) So if you (O Muhammad صلى الله عليه وسلم) are in doubt concerning that which We have revealed unto you, [i.e. that your name is written in the Taurat (Torah) and the Injeel (Gospel)], then ask those who are reading the Book [the Taurat (Torah) and the Injeel (Gospel)] before you. Verily, the truth has come to you from your Lord. So be not of those who doubt (it).

(48) No doubt! They did fold up their breasts, that they may hide from Him. Surely, even when they cover themselves with their garments, He knows what they conceal and what they reveal. Verily, He is the All-Knower of the (innermost secrets) of the breasts.

(49) But when he saw their hands went not towards it (the meal), he mistrusted them, and conceived a fear of them. They said: "Fear not, we have been sent against the people of Lut (Lot)."

(50) Indeed, We gave the Book to Musa (Moses), but differences arose therein, and had it not been for a Word that had gone forth before from your Lord, the case would have been judged between them, and indeed they are in grave doubt concerning it (this Qur'an).