“And when you sacrifice a sacrifice of thanksgiving to the LORD, you shall sacrifice it so that you may be accepted” (v29). The rules for bringing sacrifices to God’s altar taught the Israelites to approach God with respect and gratitude. They could not offer any diseased animal (v21), which would be giving God a worthless thing, rather than their best. Further, the offerings themselves were treated respectfully, not being consumed as an entitlement by anyone, but eaten by the priests and their families who had no other source of income (v10).
“I am the Lord … who brought you out of the land of Egypt” (v33). We offer the best of ourselves to God, because He gave His own life to save us.