John Wesley on Leviticus 27:29

Devoted of men - Not by men, as some would elude It; but of men, for it is manifest both from this and the foregoing verses, that men are here not the persons devoting, but devoted to destruction, either by God's sentence, as idolaters, Exo 22:20 Deu 23:15, the Canaanites, Deu 20:17, the Amalekites, Deu 25:19, and 1Sam 15:3,26, Benhaded, 1Kings 20:42, or by men, in pursuance of such a sentence of God, as Num 21:2,3 31:17, or for any crime of an high nature, as Jud 21:5 Jos 17:15. But this is not to be generally understood, as some have taken it, as if a Jew might by virtue of this Text, devote his child or his servant to the Lord, and thereby oblige himself to put them to death. For this is expressly limited to all that a man hath, or which is his, that is, which he hath a power over. But the Jews had no power over the lives of their children or servants, but were directly forbidden to take them away, by that great command, thou shalt do no murder. And seeing he that killed his servant casually by a blow with a rod was surely to be punished, as is said, Exo 21:20, it could not be lawful wilfully to take away his life upon pretence of any such vow as this. But for the Canaanites, Amalekites, &c. God the undoubted Lord of all men's lives, gave to the Israelites a power over their persons and lives, and a command to put them to death. And this verse may have a special respect to them or such as them.