Psalms 50:13 - Albert Barnes' Notes on the Bible

Will I eat the flesh of bulls, or drink the blood of goats? - This is said to show still further the absurdity of the views which seem to have prevailed among those who offered sacrifices. They offered them “as if” they were needed by God; “as if” they laid him under obligation; “as if” in some way they contributed to his happiness, or were essential to his welfare. The only supposition on which this could be true was, that he needed the flesh of the one for food, and the blood of the other for drink; or that he was sustained as creatures are. Yet this was a supposition, which, when it was stated in a formal manner, must be at once seen to be absurd; and hence the emphatic question in this verse. It may serve to illustrate this, also, to remark, that, among the pagan, the opinion did undoubtedly prevail that the gods ate and drank what was offered to them in sacrifice; whereas the truth was, that these things were consumed by the priests who attended on pagan altars, and conducted the devotions of pagan temples, and who found that it contributed much to their own support, and did much to secure the liberality of the people, to keep up the impression that what was thus offered was consumed by the gods. God appeals here to his own people in this earnest manner because it was to be presumed that “they” had higher conceptions of him than the pagan had; and that, enlightened as they were, they could not for a moment suppose these offerings necessary for him. This is one of the passages in the Old Testament which imply that God is a Spirit, and that, as such, he is to be worshipped in spirit and in truth. Compare John 4:24.