Heb 8:6, 9:15, 1 Jn 2:1, 1 Tim 2:5
In the Old Testament, Moses asked God to forgive the Israelites who had sinned. At this time, Moses became the mediator between God and the people of Israel. (Ex 32:31-32)
Ex 32:31 And Moses returned unto the Lord, and said, Oh, this people have sinned a great sin, and have made them gods of gold. 32 Yet now, if thou wilt forgive their sin--; and if not, blot me, I pray thee, out of thy book which thou hast written.
Jesus is the mediator of the better covenant that God has made. (Hebrews 8:6, Heb 9:15)
Hebrews 8:6 But now hath he obtained a more excellent ministry, by how much also he is the mediator of a better covenant, which was established upon better promises.
Heb 9:15 And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance.
When those who believe in Jesus as the Christ sin, Jesus becomes an advocate to God. (1 John 2:1)
1 John 2:1 My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:
The only mediator between God and man is Christ Jesus. (1 Tim 2:5, John 14:6)
1 Tim 2:5 For there is one God, and one mediator between God and men, the man Christ Jesus;
John 14:6 Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me.