God gave his laws to supervise us sinful Jews until Christ, Abraham’s promised descendant, would come.

Galatians 3:19-25

19 So, if someone should ask, “Why did God later give his laws to Moses?” I would reply that it was in order that people might realize how sinful they were. Those laws were valid until Jesus came. He was the descendant that God was referring to when he made the promises to Abraham. The laws were given {God gave his laws} to Moses by God’s causing angels to speak to him. Moses was the mediator, the one who told the laws to the people. 20 Now, when a mediator functions, one person is not speaking with another directly; but God himself made his promises directly to Abraham.

21 If someone should ask, “When God gave his laws to Moses long after he told Abraham what he was promising to give to him, was he changing his mind?” I would reply that God certainly did not change his mind when he did that! If God had given a law that could enable people to live eternally, then it actually would be because of people obeying that law that God would erase the record of their sins. 22 But instead, what we read in the Scriptures [PRS] is that God caused all people to be unable to escape being punished for their sins [MET], just like people in prison are unable to escape [PRS, MET]. God did that in order that he might give what he promised to those who trust Jesus Christ, just because they trust him. 23 Before God revealed the good message about trusting in Christ, the laws [PRS] that God gave to Moses were confining/imprisoning us Jews [MET], as a prisoner in jail is confined. We were unable to escape obeying those [MET] laws. This happened in order that we might believe the good message concerning Christ, the message that God would reveal later. 24 Like a father supervises his immature son by appointing a servant to take care of him [MET], God was supervising us by his laws [MET, PRS] until Christ came. He did this in order that he might erase the record of our sins only because we trust Christ. 25 But now that God has revealed the message about trusting in Christ, the laws that God gave to Moses are no longer supervising us Jews [PRS, MET].