Brothers, let me make an analogy from everyday life: when someone swears an oath, no one else can set it aside or add to it.
Now the promises were made to Avraham and to his seed. It doesn't say, "and to seeds," as if to many; on the contrary, it speaks of one - "and to your seed" - and this "one" is the Messiah.
Here is what I am saying: the legal part of the Torah, which came into being 430 years later, does not nullify an oath sworn by God, so as to abolish the promise.
For if the inheritance comes from the legal part of the Torah, it no longer comes from a promise. But God gave it to Avraham through a promise.
So then, why the legal part of the Torah? It was added in order to create transgressions, until the coming of the seed about whom the promise had been made. Moreover, it was handed down through angels and a mediator.
Now a mediator implies more than one, but God is one.
Does this mean that the legal part of the Torah stands in opposition to God's promises? Heaven forbid! For if the legal part of the Torah which God gave had had in itself the power to give life, then righteousness really would have come by legalistically following such a Torah.
But instead, the Tanakh shuts up everything under sin; so that what had been promised might be given, on the basis of Yeshua the Messiah's trusting faithfulness, to those who continue to be trustingly faithful.
Now before the time for this trusting faithfulness came, we were imprisoned in subjection to the system which results from perverting the Torah into legalism, kept under guard until this yet-to-come trusting faithfulness would be revealed.
Accordingly, the Torah functioned as a custodian until the Messiah came, so that we might be declared righteous on the ground of trusting and being faithful.
But now that the time for this trusting faithfulness has come, we are no longer under a custodian.