This is the blood of the testament which God hath enjoined unto you. – Hebrews 9:20

The blood of Jesus is the blood of the covenent. Long before this round world was made, or stars began to shine, God forsaw that He would make man. He also foresaw that man would fall into sin. Out of that fall of man His distinguishing grace and infinite sovereignty selected a multitude that no man can number to be His. But, seeing that they had offended against Him, it was necesary, in order that they might be saved, that a great scheme or plan should be devised, by which the justice of God should be fully satisfied, and yet the mercy of God should have full play. A covenant was therefore arranged between the persons of the blessed Trinity. It was agreed and solemnly pledged by the oath of the eternal Father that He would give unto the Son a multitude whom no man could number who should be His, His spouse, the members of His mystical body, His sheep, His precious jewels. These the Saviour accepted as His own, and then on His part, He undertook for them that He would keep the divine law that He would suffer all the penalties due on their behalf for offences against the law, and that He would keep and preserve every one of them until the day of His appearing. Thus stood the covenant, and on that covenant the salvation of every saved man and woman hangs…In that covenant, made between Himself and His Son, there was not a word said about our actions having any merit in them. We were regarded as though we were not, except that we stood in Christ, and we were only so far parties to the covenant as we were in the loins of Christ on that august day. We were considered to be the seed of the Lord Jesus Christ, the children of His care, the members of His own body. “According as He hath chosen us in Christ before the foundation of the world.” Oh, what grace it was that put your name and mine in the eternal roll, and provided for our salvation, provided for it by a covenant, by a sacred compact between the Father and His eternal Son, that we should belong to Him in the day when He should make up His jewels!~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/3293.cfm