Thank you for the question of animal sacrifices, “Why did God require blood sacrifices in the Old Testament? Why didn’t He just implement the new covenant in the first place instead of allowing/requiring the torture of millions of animals (for nothing, since people just went right on sinning).”
If I may share my understanding of the reason why God require blood sacrifices in the Old Testament was so that the person may see that the animal being sacrifice was to cover their sins. An innocent animal was to be sacrificed for their willful or coincidental sins against God. If an animal sacrifice was not made for their penalty of their sins, then God would require of that sinning person.
Furthermore the person who brought the animal sacrifice knew that no animal sacrifice can remove the offense before God. At best, it can only temporarily covered it. If God was to demand the life of the person who sins against their conscience or against the Law without an animal sacrifice, would anyone be left on earth? Who has sinned against another person either by thought or word. God could have spared the millions of animals but it will be a world without people.
The person in the Old Testament who brought a sin offering knew how costly it was for him. Sin was not to be taken likely for there was a high price to be paid for one’s sins just as one thinks of traffic violations. If one had to pay for every exceeding of the speed limit, failure to make a full stop, changing lanes without signaling, parking on the wrong side of the street, texting while driving, etc., the amount of debt would be astronomical. If an average traffic violation cost $100, let’s say, how many dollars would one have to pay if one wanted a clean conscience? If the patrol car doesn’t spot or cite a driver that doesn’t mean there wasn’t a traffic violation. One’s conscience knows every violation of civil law beside any moral or religious rules or laws. If one was to come clean with the civil law, most individuals would be in bankruptcy and still be in debt to the civil law.
The person in the Old Testament looked forward to a person who can remove sin by paying for its penalty and setting that person free from the debt. For no animal sacrifice can truly remove or pay the penalty for sin. No other human being can pay that debt for someone else for everyone would be under the penalty of debt. God was gracious in allowing humans to experience his grace and mercy if one would repent of one’s attitude or action.
If God was to make atonement immediate through the New Covenant, then one may never fully appreciate the sacrifice of that person to pay that debt for him/her. That person may think that it is just one little sin, but if there is an accumulation of sins/debt then that person sees his own bankruptcy and appreciates the infinite sacrifice of Jesus to remove all of that person’s sins and to give him a new life.
SUMMARY: The sacrifice of an innocent animal to cover one’s sins foreshadows a need of something or someone who can permanently remove the penalty of sin in one’s own life. The accumulation of debt allows that person to fully appreciate the sacrifice of that person to pay all of his debt. It is no small amount of debt that s/he can pay on his/her own. That person needs a Redeemer, a Savior who can satisfy the debt own to man and or to God.
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