Galatians 3:16-22 AMP

16 Now the promises (covenants, agreements) were decreed and made to Abraham and his Seed (his Offspring, his Heir). He [God] does not say, And to seeds (descendants, heirs), as if referring to many persons, but, And to your Seed (your Descendant, your Heir), obviously referring to one individual, Who is [none other than] Christ (the Messiah). [Gen. 13:15; 17:8.]

17 This is my argument: The Law, which began 430 years after the covenant [concerning the coming Messiah], does not and cannot annul the covenant previously established (ratified) by God, so as to abolish the promise and make it void. [Exod. 12:40.]

18 For if the inheritance [of the promise depends on observing] the Law [as these false teachers would like you to believe], it no longer [depends] on the promise; however, God gave it to Abraham [as a free gift solely] by virtue of His promise.

19 What then was the purpose of the Law? It was added [later on, after the promise, to disclose and expose to men their guilt] because of transgressions and [to make men more conscious of the sinfulness] of sin; and it was intended to be in effect until the Seed (the Descendant, the Heir) should come, to and concerning Whom the promise had been made. And it [the Law] was arranged and ordained and appointed through the instrumentality of angels [and was given] by the hand (in the person) of a go-between [Moses, an intermediary person between God and man].

20 Now a go-between (intermediary) has to do with and implies more than one party [there can be no mediator with just one person]. Yet God is [only] one Person [and He was the sole party in giving that promise to Abraham. But the Law was a contract between two, God and Israel; its validity was dependent on both].

21 Is the Law then contrary and opposed to the promises of God? Of course not! For if a Law had been given which could confer [spiritual] life, then righteousness and right standing with God would certainly have come by Law.

22 But the Scriptures [picture all mankind as sinners] shut up and imprisoned by sin, so that [the inheritance, blessing] which was promised through faith in Jesus Christ (the Messiah) might be given (released, delivered, and committed) to [all] those who believe [who adhere to and trust in and rely on Him].