"'"If the offering is a burnt offering from the flock, either the sheep or the goats, you are to offer a male without defect. You are to slaughter it at the north side of the altar before the Lord, and Aaron's sons the priests shall splash its blood against the sides of the altar. You are to cut it into pieces, and the priest shall arrange them, including the head and the fat, on the wood that is burning on the altar.You are to wash the internal organs and the legs with water, and the priest is to bring all of them and burn them on the altar. It is a burnt offering, a food offering, an aroma pleasing to the Lord."'" NIV translation
A sheep or goat would have been the offering of the middle class. We see that God did not hold one offering in higher regard than the other. That reminds us that it is not what we bring to God that matters; it is that we come to God with the right heart. Once again, we see that the offering covered over the stench of our sin.
"'"If the offering to the Lord is a burnt offering of birds, you are to offer a dove or a young pigeon."'" NIV translation
A bird would have been the offering of the poor and we see that poverty was not an excuse for not coming to the Lord.
"'"The priest shall bring it to the altar, wring off its head and burn it on the altar; its blood shall be drained out on the side of the altar. He is to remove the crop and the feathers and throw them down east of the altar where the ashes are. He shall tear it open by the wings, not dividing it completely, and then the priest shall burn it on the wood that is burning on the altar. It is a burnt offering, a food offering, an aroma pleasing to the Lord."'" NIV translation
The main difference between the offerings was that the priests were to kill the birds instead of the person that brought them. This is a reminder to us that, even when it seems like we do not have the strength to come to Him, He has made a way through Jesus Christ.