When the forty (40) days prescribed by the law of Moses for the purification of the mother of a newborn son were accomplished (Leviticus 12:2-4), the All-Holy Mother of God and Saint Joseph brought the Child Jesus to Jerusalem to present Him to the Lord. For every first-born, belonging by right to the Lord (Exodus 13:15), had to be consecrated to Him in the Temple and be, in a way, exchanged for the offering in sacrifice of a yearling lamb or, for poor families, of two turtle-doves or two pigeons (Leviticus 12:8).