"And I will make an everlasting covenant with them, that I will not turn away from them, to do them good; but I will put my fear in their hearts, that they shall not depart from me." (Jeremiah 32: 40)
Here we find another reference and promise of God's New Covenant with Israel, and thus with all who believe on His Son Jesus:
"And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together." (Romans 8: 17)
"That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel: (Ephesians 3: 6)
So, we can enjoy the same promises which God made through Jeremiah to the Israelites.
Now, in this affirmation of the Gospel, God speaks of an everlasting covenant.
One which does not depend on us, this everlasting covenant depends on the blood of Jesus:
"And he said unto them, This is my blood of the new testament, which is shed for many." (Mark 14: 24)
This blood is perfect, and cleanses forever more:
"Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation received by tradition from your fathers; 19But with the precious blood of Christ, as of a lamb without blemish and without spot:" (1 Peter 1: 18-19)
"But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin." (1 John 1: 7)
This New Covenant, grants to us a new heart, one which allows God to cause us to walk in His ways, too! Why? Because we know that we are forgiven:
"But there is forgiveness with thee, that thou mayest be feared." (Psalm 130: 4)
This forgiveness comes through His Son, and thus He is faithful and just to forgive us all our sins, and thus cause us to fear Him!