What is a covenant? It is a special, formal arrangement between two parties wherein both parties have clearly defined responsibilities. The benefits of keeping the covenant and the consequences of breaking it are laid out so that both parties enter it with eyes wide open. God makes covenants with man. He does not make contracts. The difference is that contracts are based on a lack of trust. Trust is the basis of all relationships. God does not want a contract with us. He wants relationship. He wants to be our Father. A contract says, "I don't really trust you to do the right thing, so I'm making you put it on paper so I can hold you accountable if and when you don't".
People that make pre-nuptual contracts are basing their relationship on a lack of trust, and they are basically leaving the back door of exit open before the marriage even begins. Marriage is a covenant between a man and a woman, and it was designed by God in the beginning, not by man (Genesis 1-2, Matthew 19:3-9). We should not be surprised by the recent redefining of marriage by the courts. They have been redefining marriage for decades. Once man moves off of the foundation of the Bible, the only other option is that which is made up by man. That is fickle, false, arbitrary, and doomed to fail. We call ourselves a nation under God, but the courts have not been under God for decades, although there are still displays in them that profess this. Our Constitution was based on the Bible, but many judges do not even believe in the Constitution because they do not believe in the Bible. Like a father/son relationship is to be symbolic of our relationship with God, so is marriage (Ephesians 5:22-33).
God has made different covenants with man a various times. He made a covenant with Adam and Eve (Genesis 2). He made a covenant with Noah (Genesis 9). He made a covenant with Abraham (Gen 12-22). God progressively revealed the details of this covenant, and the meeting God had with Abraham in Genesis 15 is interesting. God told Abraham to cut animals into two and to lay out the halves on the ground. This sounds a little disgusting to some people, but this was how people entered into the most serious of covenants together. They would walk through the pieces and bind themselves together by blood. The original Hebrew of the Old Testament actually says they would cut a covenant, not make a covenant. God also made a covenant with the nation of Israel on Mount Sinai when He gave Moses the law. Leviticus 26 and Deuteronomy 28 make clear the covenant responsibilities, the benefits, and the consequences. Notice there are no consequences for God because He never fails to keep His part of the covenant. He is faithful. It is man that fails. God knew man was going to fail. Note that God did not say if they failed , but when.
Therefore God predetermined that there would be a new covenant. Another word for covenant is testament. That is why we call the second part of the Bible the New Testament. This testament like the old one was sealed in blood, but it was not just the blood of animals. It was the priceless blood of Jesus Christ (Matthew 26:28, 1Peter 1:18-19). A testament does not go into effect until after the death of the testator (Hebrews 9"13-23). Then comes the reading of the will (another word for testament). This occurred in Acts 2 when the disciples received the baptism of the Holy Ghost and spoke with tongues and Peter "read the will" to the people by telling them the gospel of the death, burial, and resurrection of Jesus Christ. They asked what to do, and he told them, "Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.". This is how the blood of the covenant is applied to us.
The law of Moses did not fail and need to be superseded by a new covenant because there was something wrong with the word of God. It failed to produce what God was looking for because the sinful nature of man causes him to come short of keeping his part of the covenant (Romans 3). So God made a new covenant. Jeremiah said that in this one God does not just speak His word from a mountain or write in on tables of stone. He writes it in our hearts (Jeremiah 31:31-34, 2Corinthians 3:3, Hebrews 8:6-13). We become partakers of the divine nature by Him putting His Spirit within us (2Peter 1:1-11). We do not have to rely on our own efforts to be religious. God fills us with His Spirit and empowers us to fulfill our part of the covenant. His part of the covenant is much bigger than our part, but we must learn to have His grace help us do that which we cannot do on our own. His commandments are not optional, but they are not grievous (1John 5:3). In the "sermon on the mount" (Matthew 5-7), Jesus did not dismiss the old covenant, He showed us that He wants to take us to the spiritual fulfillment of it. Now He can do that from the inside out by the gift of His Spirit.