John 8:57

This, however, the Jews completely misunderstand. They think that by asserting that Abraham saw His day, Jesus means to say that His day and the life of Abraham on earth were contemporaneous. Πεντήκοντα … ἑώρακας; “Fifty years” may be used as a round number, sufficiently exact for their purpose and with no intention to determine the age of Jesus. But Lightfoot (Hor. Heb., 1046) thinks the saying is ruled by the age when Levites retired, see Numbers 4:3; Numbers 4:39 : “Tu non adhuc pervenisti ad vulgarem annum superannuationis, et tune vidisti Abrahamum?” Irenaeus (ii. 22, 5) records that the Gospel (presumably this passage) and the Presbyters of Asia Minor who had known John, testified that Jesus taught till He was forty or fifty. This idea is upheld by E. v. Bunsen (Hidden Wisdom of Christ), and even Keim is of opinion that Jesus may have lived to His fortieth year.