Jamieson, Fausset and Brown on Isaiah 66:3

3. God loathes even the sacrifices of the wicked (Is 1:11; Pr 15:8; 28:9).

is as if--Lowth not so well omits these words: "He that killeth an ox (presently after) murders a man" (as in Eze 23:39). But the omission in the Hebrew of "is as if"--increases the force of the comparison. Human victims were often offered by the heathen.

dog's neck--an abomination according to the Jewish law (De 23:18); perhaps made so, because dogs were venerated in Egypt. He does not honor this abomination by using the word "sacrifice," but uses the degrading term, "cut off a dog's neck" (Ex 13:13; 34:20). Dogs as unclean are associated with swine (Mt 7:6; 2Pe 2:22).

oblation--unbloody: in antithesis to "swine's blood" (Is 65:4).

burneth--Hebrew, "he who offereth as a memorial oblation" (Le 2:2).

they have chosen--opposed to the two first clauses of Is 66:4: "as they have chosen their own ways, &c., so I will choose their delusions.