The Old Testament passage being quoted is from Lev. 12:6-8. There the Lord commanded a lamb and a young pigeon or a turtledove as the prescribed sacrifice. If the woman was unable to offer a lamb, then two young pigeons or two turtledoves were acceptable. Mary would not have offered the lesser offering if it had been in her power to provide the lamb.
This reveals that Joseph and Mary were not well off financially, yet the Lord chose them to be the earthly parents of His only begotten Son.
The Lord doesn’t choose the way man chooses. Man looks on the outward appearance but God looks on the heart (1 Sam. 16:7).
Mary and Joseph were chosen when they were without: without fame, without position, without money. God entrusted the most precious gift He had to a couple who would surely have been overlooked if men had been conducting the search.
God isn’t looking for ability, but rather availability. D. L. Moody once heard a preacher say, ‘The world has never seen what God can do with one man who is totally yielded to Him.’ In response, D. L. said, ‘By the grace of God, I’ll be that man.’ This uneducated man went on to shake three continents for God.
God will choose you too, if you’ll make yourself available to Him (1 Cor. 1:26-28).