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.
Romans 9:8
This means that it is not the physical descendants [of Abraham] who are God's children, but it is the children [born] according to [God's] promise who are [Abraham's true] descendants.
Galatians 4:28
Now, brothers, you [Christians] are children of the promise [made to Abraham. See 3:29] just like Isaac, [Abraham's son] was.
Hebrews 11:13
These people [all] continued to have faith until they died, [even though] they had not obtained [all] the things God had promised, but had [only] seen them and welcomed them from a distance. And they had confessed to being strangers and aliens on earth.