The 80th mitzvah is that we are commanded to redeem a first-born male and to give the redemption value to a kohen.
The source of this commandment is G‑d's statement,1 "Give Me the first-born of your sons." The explanation of this "giving" is that we must redeem him as if the kohen already owns him. We acquire the child from the kohen by giving him five selah.
The source of this commandment is G‑d's statement,2 "You must redeem a first-born male child."
This mitzvah is called pidyon haben. Women are not obligated in this mitzvah; it is the child's mitzvah which the father must fulfill, as explained in Kiddushin.3
The details of this mitzvah are explained in tractate B'choros.
Levites are exempt from this mitzvah.
