Leviticus 1:10 (ESV)
10 “If his gift for a burnt offering is from the flock, from the sheep or goats, he shall bring a male without blemish,
An animal without defect was one that was prized. In particular, male animals without defect would be used to populate the flock in future years. It was a real sacrifice to present such animals to the slaughter. Many years later, the prophet Malachi tells the nation of Judah that they despise the Lord and profane his table because their animals were inferior (Malachi 1:7–13).
3 “If his offering is a burnt offering from the herd, he shall offer a male without blemish. He shall bring it to the entrance of the tent of meeting, that he may be accepted before the LORD.