And to offer a sacrifice according to that which is said in the law of the Lord, A pair of turtledoves, or two young pigeons.
Note 2 at Lu 2:24: God's first choice for this offering of purification was a lamb and a young pigeon or turtledove (Le 12:6). However, if a woman was unable to provide a lamb for a burnt offering, she could offer a pair of turtledoves or two young pigeons (Le 12:8). This indicates Joseph and Mary's financial condition. They would never have offered the humbler sacrifice if the lamb had been within their means.