God commanded that the animals sacrificed to him be free of any defects. Sometimes the Israelites failed to do this. Here is what the prophet Malachi said about their failure.
A son honors his father, and a servant his master. If then I am a father, where is my honor? And if I am a master, where is my fear? says the LORD of hosts to you, O priests, who despise my name.
But you say, “How have we despised your name?” By offering polluted food upon my altar. But you say, “How have we polluted you?” By saying that the LORD’s table may be despised. When you offer blind animals in sacrifice, is that not evil? And when you offer those that are lame or sick, is that not evil?
He gave them a standard by which they could measure the acceptability of their offerings.
Present that to your governor; will he accept you or show you favor? says the LORD of hosts.