Marlin said:
The Law of Moses demanded physical ritual sacrifices, but was "weak and useless" to fully save its practitioners because it didn't require the heart. "To obey is better than to sacrifice," says the scripture.
You are mixing up
covenant and
law. Both have the same purpose, but one addresses our actions, while the other describes God's actions.
The awareness that ritual sacrifice wasn't enough was already there long before Christ came along, and the prophets made sure everyone heard it. You say the law didn't require heart. But the law was "Love the LORD your God with all your heart and with all your soul and with all your strength" (Deut. 6:5; Joshua 22:5) and "Love your neighbour as yourself" (Lev. 19:18) - Jesus only confirmed this, adding that "all the Law and the Prophets hang on these two commandments". So the law
did require heart. The weakness was that
we could not supply it - laws written on stone created hearts of stone, and we could not obey the words of the covenant. We didn't
have the heart, and that made every attempt to meet God's requirements insufficient.
Romans 8:3
For what the law was powerless to do in that it was weakened by the sinful nature, God did by sending his own Son in the likeness of sinful man to be a sin offering.
The new covenant required a sacrifice of a broken heart and a contrite spirit, with a full commitment to living the gospel, rather than just killing animals. The Law of Moses was unable to fully save anyone, yet it was given to the Israelites because they couldn't handle the higher law. Thus the "former regulations" (the Law of Moses) weren't enough to bestow eternal life on anyone, but rather they pointed ahead to Christ in anticipation of the higher laws being given.
So did the old covenant. But it was insufficient
because it depended on men.
Hebrews 7:28
For the law appoints as high priests men who are weak; but the oath, which came after the law, appointed the Son, who has been made perfect forever.
If the Israelites under the direction and authority of Moses, Aaron and the Levites were unable to meet its requirements, how much less would we be able to meet the intention of the law - the "higher" law Jesus explained in His sermon on the Mount? Our righteousness would have to surpass even the
teachers of the law! And Jesus did not abolish this law, He just fulfilled it (Matt. 5:17).
The law and prophets pointed to Christ, certainly, but not to even higher laws than the ones we already could not handle. The knowledge of more righteous laws does not make someone more able to meet them (i.e. a more righteous
person), that was their weakness. Laws point out sin, but cannot make us righteous.
Romans 3:20-22
Therefore no one will be declared righteous in his sight by observing the law; rather, through the law we become conscious of sin.
But now a righteousness from God, apart from law, has been made known, to which the Law and the Prophets testify. This righteousness from God comes through faith in Jesus Christ to all who believe.
(Phil. 3:8-10) What is more, I consider everything a loss compared to the surpassing greatness of knowing Christ Jesus my Lord, for whose sake I have lost all things. I consider them rubbish, that I may gain Christ and be found in him, not having a righteousness of my own that comes from the law, but that which is through faith in Christ — the righteousness that comes from God and is by faith.