The word(s) "once" appears 119 time(s) in 116 verse(s) in Quran in Abdullah Yusuf Ali translation.

(51) For each (such person) there are (angels) in succession, before and behind him: They guard him by command of Allah. Allah does not change a people's lot unless they change what is in their hearts. But when (once) Allah willeth a people's punishment, there can be no turning it back, nor will they find, besides Him, any to protect.

(52) "O our Lord! truly Thou dost know what we conceal and what we reveal: for nothing whatever is hidden from Allah, whether on earth or in heaven.

(53) And Allah doth know what ye conceal, and what ye reveal.

(54) Undoubtedly Allah doth know what they conceal, and what they reveal: verily He loveth not the arrogant.

(55) Then, on the Day of Judgment, He will cover them with shame, and say: "Where are My 'partners' concerning whom ye used to dispute (with the godly)?" Those endued with knowledge will say: "This Day, indeed, are the Unbelievers covered with shame and misery,-

(56) They ask thee concerning the Spirit (of inspiration). Say: "The Spirit (cometh) by command of my Lord: of knowledge it is only a little that is communicated to you, (O men!)"

(57) (Some) say they were three, the dog being the fourth among them; (others) say they were five, the dog being the sixth,- doubtfully guessing at the unknown; (yet others) say they were seven, the dog being the eighth. Say thou: "My Lord knoweth best their number; It is but few that know their (real case)." Enter not, therefore, into controversies concerning them, except on a matter that is clear, nor consult any of them about (the affair of) the Sleepers.

(58) But your Lord is Most forgiving, full of Mercy. If He were to call them (at once) to account for what they have earned, then surely He would have hastened their punishment: but they have their appointed time, beyond which they will find no refuge.

(59) The other said: "If then thou wouldst follow me, ask me no questions about anything until I myself speak to thee concerning it."

(60) They ask thee concerning Zul-qarnain. Say, "I will rehearse to you something of his story."