Does the Bible say 'once a man twice a child'?

No, that phrase is not in The Bible.

AnswerThis was quoted by a Rabbi (Jewish faith.) It means that a man (this should include women) is born, becomes a man and is strong only to grow older and face death where he is treated at home or in a nursing home and thus is reformed either from disease or the way he has to be looked after in old age as a child yet once again.

Answer

It is not in the Bible, but it is a very old saying, most popularly taken from Hamlet, Act II, Scene II, but at least as old as Sophocles [c. 450BC].

One of the 'church fathers,' Clement of Alexandria, writing around 200AD on the subject of plagiarism, writes this:

Theopompus [c. 350BC] having written:-"Twice children are old men in very truth; " And before him Sophocles [c. 450BC] in Peleus:- "Peleus, the son of Aeacus, I, sole housekeeper, Guide, old as he is now, and train again, For the aged man is once again a child,"- Antipho the orator [c. 430BC] says, "For the nursing of the old is like the nursing of children." Also the philosopher Plato [c. 400BC] says, "The old man then, as seems, will be twice a child.

(from the Stromata, or Miscellanies, Book VI, Chapter II)

It is also quoted in the Jewish Midrash "Genesis Rabbah" (pg. 62) which would be dated somewhere around 500AD; it appears to be a reference to Lot, as it's referring to his descendants, the Ammonites and Moabites, but is contained in a larger section of commentary on Gen. 14.