Treasury of Scripture Knowledge

Summary

For if the inheritance be of the law, it is no more of promise: but God gave it to Abraham by promise.

Bible References

If

Galatians 3:10
For all who seek to be right with God by trying to meet all the requirements of the law of Moses are under a curse [from God], because it is written [Deut. 27:26], "Every person is cursed [i.e., cut off from God] who does not continue to obey all of the requirements written in the law of Moses."
Galatians 2:21
[In doing this] I am not trying to disregard God's unearned favor, for if a person could become right with God by [perfect obedience to the requirements of] the law of Moses, then Christ died for nothing.
Romans 4:13
For it was not through [obedience to] law [See 3:31] that the promise to Abraham or his descendants of inheriting [the best of] the world [was made], but through their being considered righteous because of faith [in God].
Romans 8:17
And if we are [His] children, then we have an inheritance from God [i.e., blessings here and hereafter] and are fellow-sharers with Christ [of such blessings], providing we [are willing to] suffer with Him, so we can also be honored with Him [i.e., in the future life. See verses 18-25].

But

Galatians 3:16
Now [specific] promises were made to Abraham and to his seed [i.e., descendants]. [God] did not say "seeds" [plural] as though He were referring to many persons but "seed" [singular] showing that He meant one [descendant]; [Gen. 13:15 says] "And to your seed," referring to Christ.
Luke 1:54
(As He said to our forefathers), He has helped His servants, the Israelites, [showing] that He remembered to be merciful
Hebrews 6:12
We do not want you people to be [spiritually] slack, but to imitate those who will inherit [God's] promises because of their faith and patience.