The word(s) "once" appears 85 time(s) in 79 verse(s) in Quran in Muhammad Habib Shakir translation.

(21) O followers of the Book! indeed Our Apostle has come to you making clear to you much of what you concealed of the Book and passing over much; indeed, there has come to you light and a clear Book from Allah;

(22) And when they come to you, they say: We believe; and indeed they come in with unbelief and indeed they go forth with it; and Allah knows best what they concealed.

(23) Nay, what they concealed before shall become manifest to them; and if they were sent back, they would certainly go back to that which they are forbidden, and most surely they are liars.

(24) And they do not assign to Allah the attributes due to Him when they say: Allah has not revealed anything to a mortal. Say: Who revealed the Book which Musa brought, a light and a guidance to men, which you make into scattered writings which you show while you conceal much? And you were taught what you did not know, (neither) you nor your fathers. Say: Allah then leave them sporting in their vain discourses.

(25) Say: Come I will recite what your Lord has forbidden to you-- (remember) that you do not associate anything with Him and show kindness to your parents, and do not slay your children for (fear of) poverty-- We provide for you and for them-- and do not draw nigh to indecencies, those of them which are apparent and those which are concealed, and do not kill the soul which Allah has forbidden except for the requirements of justice; this He has enjoined you with that you may understand.

(26) Surely they who divided their religion into parts and became sects, you have no concern with them; their affair is only with Allah, then He will inform them of what they did.

(27) Say: My Lord has only prohibited indecencies, those of them that are apparent as well as those that are concealed, and sin and rebellion without justice, and that you associate with Allah that for which He has not sent down any authority, and that you say against Allah what you do not know.

(28) Do they not see that they are tried once or twice in every year, yet they do not turn (to Allah) nor do they mind.

(29) And people are naught but a single nation, so they disagree; and had not a word already gone forth from your Lord, the matter would have certainly been decided between them in respect of that concerning which they disagree.

(30) And you are not (engaged) in any affair, nor do you recite concerning it any portion of the Quran, nor do you do any work but We are witnesses over you when you enter into it, and there does not lie concealed from your Lord the weight of an atom in the earth or in the heaven, nor any thing less than that nor greater, but it is in a clear book.