John 3:4

4. How… be born To be born again was a figure familiar with the Jews, even, it is said, of our Lord’s day. When a proselyte was admitted into Judaism, so new were his relations and feelings that he was said to be a newborn babe. Abraham when circumcised was “born again.” It applied not only to a change of relations, (like our American naturalization of a foreigner,) but to his opinions and feelings.

Hence, many modern commentators endeavour to so interpret Nicodemus’s words as not to imply that he imagined Jesus to refer to a bodily new birth. But it is clear, from his very explicit language, that he thought our Lord’s description of this being born again to be so radical and absolute as to suggest and justify the query whether it did not include a re-birth of body. He did so, perhaps, from three reasons. 1. The words of Jesus seem to imply, not merely, as among the Jews, a change of relations, feelings, or opinions; but some renovation of nature deeper and underlying all these, and coming from an external agent. 2. The kingdom of God, of which this renovation was necessary to the seeing, is to be itself brought in by a renovation, which was held by most Jews to include a physical renewal of the earth. How physical and bodily, then, might not the regeneration it required of its individual subjects be? 3. This regeneration was a new and unheard-of one; required, not like Jewish regeneration, of Gentiles alone, but a regeneration even of the chosen seed. How deep then is it, and how can it be brought about? Is it bodily, and if so, how can it be effected?

When he is old As Nicodemus himself may have been; though this is not so certain as commentators seem to imply. He may have been as young as John himself, and like him have survived the destruction of Jerusalem. See note on John 3:1.