Pidyon haben, the redemption of the son, is the rite in which the father of a firstborn son redeems him from a priest (kohen) on the thirty-first day after birth, paying the value of five silver shekels. It rests on the biblical teaching that the firstborn of Israel belong to God, a claim connected to the sparing of the Israelite firstborn in Egypt, and were originally destined for divine service, a role later transferred to the tribe of Levi, so that other firstborn sons must be symbolically bought back.
The ceremony is short: the father presents the child, declares his obligation, and hands the redemption money to the kohen, who pronounces a blessing. It applies only in specific cases, the son must be the mother's first child, born naturally, and neither parent of priestly or Levite descent, so many families never perform it, which lends the occasion, when it does occur, a particular rarity.