Jer 31:31-32 "Behold, the days are coming, says the Lord, when I will make a new covenant with the house of Israel and with the house of Judah— not according to the covenant that I made with their fathers in the day that I took them by the hand to lead them out of the land of Egypt, *My covenant which they broke, though I was a husband to them,* says the Lord."
Adam's descendents were failures even with the knowledge of good and evil. Abraham's descendents too were failures for they broke the Abrahamic covenant (Mosiac Law), though God was in their midst. Their hearts were blinded with selfishness and wickedness, that they refused to reciprocate to God's love, care and concern. God was like a husband to them, giving them the chance to be His bride but out of unbelief they rejected Him and broke the covenant. To ensure that the Israelites conform to His image in order to be His bride, He made the Old Covenant obsolete, and made a New Covenant with them
New Spirit in New Covenant
Eze 11:19 "Then I will give them one heart, and I will put a new spirit within them, and take the stony heart out of their flesh, and give them a heart of flesh"
Our Lord Jesus was born in humility and filled with grace and truth. Out of his love, He offered Himself on the cross as our sacrificial Lamb. The disciples of Jesus (all Jews), who followed Him were given the New Spirit (Spirit of Christ), thus fulfilling the prophecies. Unfortunately, the Priesthood, Pharisees and Scribes rejected Him for they loved the world and the things therein more than Yahweh and Messiah.
Spirit of Christ
I Pet 1:10-11 Of this salvation the prophets have inquired and searched carefully, who prophesied of the grace that would come to you, searching what, or what manner of time, the Spirit of Christ who was in them was indicating when He testified beforehand the sufferings of Christ and the glories that would follow.
With the Spirit of Christ, His disciples will rejoice for being a partaker of His sufferings.
Spirit of Truth
John 14:15-17a, 26; 16:13 "If you love Me, keep My commandments. And I will pray the Father, and He will give you another Helper, that He may abide with you forever— the Spirit of truth... He will teach you all things, and bring to your remembrance all things that I said to you... However, when He, the Spirit of truth, has come, He will guide you into all truth; for He will not speak on His own authority, but whatever He hears He will speak; and He will tell you things to come.
The Spirit of truth is also the New Spirit for it is given only to those who keeps the commandments of our Lord Jesus. With truth in them, they will be set free from their bondages i.e their love of the world and the things therein - the lust of the eyes, the lust of the flesh and the pride of life.
Rom 8:11 But if the Spirit of Him who raised Jesus from the dead dwells in you, He who raised Christ from the dead will also give life to your mortal bodies through His Spirit who dwells in you.
Jesus - Finisher of our Faith
Heb 12:2 looking unto Jesus, the author and finisher of our faith, who for the joy that was set before Him endured the cross, despising the shame, and has sat down at the right hand of the throne of God.
Brethren, we only need to believe who Jesus is and keep His words and commandments, and He will give us the Spirit of Christ, who will transform us into His image and bride of the Lamb. The Epistles of the Apostles will guide and enlighten His truth.