Nicodemus used this question to emphasize that this could not happen. AT: "A man certainly cannot be born again when he is old!" (See: [[rc://en/ta/man/translate/figs-rquestion]])
Nicodemus also used this question to emphasize his belief that a second birth was impossible. "Certainly, he cannot enter a second time into his mother's womb! (See: [[rc://en/ta/man/translate/figs-rquestion]])