Q. How old was Jesus at his presentation at the temple?
Since Luke tells us that Mary and Joseph offered “a sacrifice in keeping with what is said in the Law of the Lord: ‘a pair of doves or two young pigeons,'” we know that Mary was performing the ceremony for purification after childbirth, as described in Leviticus. There we read, “A woman who . . . gives birth to a son will be ceremonially unclean for seven days . . . On the eighth day the boy is to be circumcised. Then the woman must wait thirty-three days to be purified. . . . When the days of her purification for a son or daughter are over, she is to bring to the priest at the entrance to the tent of meeting a year-old lamb for a burnt offering and a young pigeon or a dove for a sin offering. . . But if she cannot afford a lamb, she is to bring two doves or two young pigeons, one for a burnt offering and the other for a sin offering.”
So we know from this that Jesus was 7 + 33 = 40 days old at the time of this ceremony. (We know that the eighth day after birth is the first of the following 33 days because the account also says that after the birth of a daughter a mother waits twice as long, specifically 14 + 66 = 80 days.)
It’s interesting to compare Mary’s 40 days of waiting to dedicate Jesus, during which she no doubt continued to “treasure up” all the events surrounding his birth and “ponder them in her heart,” with Jesus’ 40 days of testing in the wilderness as he prepared to take on his role as the Messiah. In fact, for Jesus himself this time right after his birth was 40 initial days of waiting to assume a life dedicated to God.