I ask you again, does God give you the Holy Spirit and work miracles among you because you obey the law? Of course not! It is because you believe the message you heard about Christ.
Now a mediator is helpful if more than one party must reach an agreement. But God, who is one, did not use a mediator when he gave his promise to Abraham.
For you are all children of God through faith in Christ Jesus. And all who have been united with Christ in baptism have put on Christ, like putting on new clothes.