As we come to study the new and old testaments, we must first know the difference between these terms: a promise, an oath, a covenant, and a testament. A promise is an ordinary word spoken by God, promising you that He will do something for you. An oath is a confirmation of God’s word of promise. God confirmed His word of promise by means of His oath (Heb. 6:13, 17). When a promise is confirmed by an oath, it immediately becomes a covenant. What we have received from God is not merely an ordinary word of promise but a covenant confirmed by God’s oath and sealed with His faithfulness. When the One who made the covenant died, the covenant became a bequeathed will, that is, a testament. Today the covenant is no longer merely a covenant but a testament bequeathed by the One who enacted the covenant.
The new testament and the old testament are the two covenants which God made with man as the two conditions upon which man may have a relationship with Him. The new testament is a continuation of the covenant God made with Abraham. In Genesis chapter twelve, God gave a promise to Abraham and later also swore to him (Gen. 22:16). Hence, the promise became a covenant made by God with Abraham (Gal. 3:15-17). Two thousand years later, God sent His Son Jesus Christ to the world, who shed His blood on the cross and enacted the new covenant (Luke 22:20). At that point the new covenant was accomplished; moreover, it became a testament because of the Lord’s death.
The old covenant, which came four hundred and thirty years after God made the covenant with Abraham, was enacted at Mount Sinai, where God gave the law to the children of Israel. Strictly speaking, the old covenant does not cover the entire period of the Old Testament, from Genesis to Malachi. It actually began from Exodus 19 and continued until the time of John the Baptist (Matt. 11:12-13). The time of John the Baptist to the time before the death and resurrection of the Lord Jesus is a transitional period between the Old and the New Testament times. Whereas God dealt with man in the Old Testament according to the old covenant—the law, He deals with man in the New Testament according to the new covenant— grace.
Romans 5:20 says that “the law entered.” This word means that the law was not in God’s original intention, nor was it God’s original ordination for man. Rather, it entered later; it was added along the way. In the beginning God did not have any intention to deal with man according to the law; rather, the law was added later because of man’s fall and corruption.
After rescuing the children of Israel from Egypt and bringing them to the foot of Mount Sinai, God told them that He had borne them on eagles’ wings when He brought them out of Egypt (Exo. 19:4). God was speaking words of grace to the children of Israel, telling them that what He had done to them was a matter of grace. If they had known themselves, they would have trusted in Him and would have asked Him to continue to deal with them according to grace and to take care of them in everything. But, since at that time they did not know themselves, they neither respected nor trusted in His grace. On the contrary, they trusted in themselves and told God that all He had commanded they would do (Exo. 19:7-8). Because they were so ignorant concerning themselves, thinking they could do what God had commanded, God changed His attitude toward them and gave them the law.
In the beginning God dealt with them according to grace; like an eagle with her young, He was very pleasant and approachable. But when He changed His attitude and began to deal with them according to the law, He came to them in a flame of fire and became dreadful and terrifying. God changed His attitude toward them and dealt with them according to the law so that He might make manifest their transgressions and expose their real condition through the law, that they might know their inability to keep God’s commands, and that they might realize their wickedness and impotence (Rom. 3:20).
Since the old covenant was something added and was not God’s original intention for man, it could not remain permanently. Rather, it became old, grew decrepit, and disappeared (Heb. 8:13). Moreover, the glory of the ministry of the old covenant was also done away (2 Cor. 3:7).