Now this was the victim of the poor. For the Lord commanded in the law that they who were able should offer a lamb for a son or a daughter as well as a turtle dove or pigeon; but they who were not able to offer a lamb should give two turtle doves or two young pigeons. Therefore the Lord, though he was rich, deigned to become poor, that by his poverty He might make us partakers of His riches.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Hom. Purif.