Leviticus 19:5

And when you sacrifice the consecrated victims before the Lord, you shall make the sacrifice acceptable.

If you sacrifice a peace-offering This is connected to the previous verse: They shall not offer sacrifices to the demons, who are false gods, but rather shall offer sacrifices only to God. The verb sacrifice is in plural form, because Scripture speaks of the most common case, when several people join together to offer a single sacrifice.

of your own free will They should bring the sacrifice willingly, and not out of compulsion.

He states, And when ye offer an offering of peace-offerings unto the Eternal etc., for after He prohibited the slaughtering of sacrifices, and all manner of worship to idols and to molten gods, and ordered that all Services be devoted to the Proper Name [i.e., the Tetragrammaton] exclusively, He stated here that when you shall bring an offering to the Eternal, it shall be lirtzonchem [“of your desire”], in order that your worship should be acceptable to Him and that He should be pleased with you, even as a servant reconciles himself to his master by doing all that he commands him to do, the expression [lirtzonchem] being similar to: ‘v’nirtzah’ (and it shall be accepted) for him to make atonement for him; but by the light of Thy countenance, because ‘retzitham’ (Thou wast favorable unto them). … And the meaning of the verse is to state that you are not to think that there is any benefit in idol worship, neither are you to do the service of the Glorious Name in order to receive a reward, but only to do His Will, for it is His simple Will that is proper and incumbent upon us [to do]. He states this with reference to the peace-offerings because they are of the lesser degree of holy offerings, which are eaten by the owners themselves [unlike the most holy offerings, such as the sin-offering, which may be eaten only by the priests, the verse thus saying] that the owners are to guard their thoughts, so that the offerings be brought with the proper intention, and this applies all the more so to the most holy offerings. Or it may be that [the verse here mentions peace-offerings] because peace-offerings are the [unique] attribute of Israel, just as our Rabbis have said: “Noachides did not offer peace-offerings.” The student learned [in the mysteries of the Cabala] will understand. And our Rabbis have said: “Lirtzonchem [literally: ‘to your intent’] slaughter the offering, meaning that you are to have the intention to slaughter it,” for if he merely “handles” an offering [i.e., if he does the act of slaughtering without the intention of so doing], he invalidates [the offering].

לרצונכם, by ensuring the animal is unblemished and the procedure of semichah, placing one’s weight on it with one’s hands has been performed, as well as all the other details which have been spelled out in Leviticus 3,6.

וכי תזבחו, at this point the Torah explains that when G’d issued the very first of the Ten Commandments with the words: “I am the Lord your G’d, etc.,” (20,2) this meant that the Israelites must accept Him as the exclusive divine power in the universe. They are to do so without reservation, just as they did during the song of thanksgiving for their miraculous salvation after crossing the sea with dry feet, when they sang (Exodus 15,2) זה א-לי ואנוהו, אלוקי אבי וארוממנהו, “this is My G’d and I will enshrine Him, the G’d of my forefather and I will exalt Him.” Not only must the Jewish people accept G’d’s dictates and carry them out, but they must be concerned with preserving His great name and not even in their thoughts do anything which would desecrate this great name of His.