Charles Ellicott Commentary Leviticus 19:5

"And when ye offer a sacrifice of peace-offerings unto Jehovah, ye shall offer it that ye may be accepted." — Leviticus 19:5 (ASV)

And if you offer a sacrifice. — From Leviticus 17:3-7, it can be seen that the Israelites were in the habit of sacrificing to idols the animals intended for private consumption, and that this practice gave rise to the enactment that when any of the three kinds of quadrupeds were to be slaughtered for daily meat, they should first be devoted to God as peace offerings. Therefore, the transition here is from the prohibition of idolatrous worship to the peace offerings. The simple abstention from sacrificing to idols and offering them to God is not enough. If the Israelites bring a peace offering to the Lord, it must be offered in the prescribed manner.

You shall offer it at your own will. — Better, you shall offer it for your acceptance ; that is, you are to do it in such a manner as will secure for you Divine acceptance.