Romans 9:7

they are not all children of Abraham because they are Abraham's descendants. The promise was, In Isaac shall thy posterity be called.

Hebrews 11:18

of whom it had been said, It is through Isaac that your posterity will be traced.

Luke 3:8

Then bring forth fruit befitting your penitence, and do not begin to say to yourselves, "We have Abraham as our father." I tell you that God is able to raise up sons to Abraham out of these stones.

Luke 16:24-25

"And he cried out and said, 'Father Abraham have mercy on me; and send Lazarus to dip the tip of his finger in water and cool my tongue, for I am in anguish in this flame.'

Luke 16:30

"'Nay, Father Abraham,' he said 'but if some one went to them from the dead they would repent.'

John 8:33

"We are descendants of Abraham," they replied, "and have never been in slavery to any man. What do you mean by saying, 'You shall become free'?"

John 8:37-39

"I know you are Abraham's descendants; but you are seeking to kill me, Because my teaching has no place in you.

Galatians 4:23

but while the son by the slave woman was born according to the flesh, the son by the free woman was born in fulfilment of a promise.

Philippians 3:3

For we are the true circumcision, who worship God in the spirit, and make our boast in Christ Jesus, and have no confidence in outward rites,

Treasury of Scripture Knowledge

Summary

Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called.

In isaac

Bible References

Because

Luke 3:8
Then bring forth fruit befitting your penitence, and do not begin to say to yourselves, "We have Abraham as our father." I tell you that God is able to raise up sons to Abraham out of these stones.
Luke 16:24
"And he cried out and said, 'Father Abraham have mercy on me; and send Lazarus to dip the tip of his finger in water and cool my tongue, for I am in anguish in this flame.'
John 8:37
"I know you are Abraham's descendants; but you are seeking to kill me, Because my teaching has no place in you.
Philippians 3:3
For we are the true circumcision, who worship God in the spirit, and make our boast in Christ Jesus, and have no confidence in outward rites,

In isaac

Hebrews 11:18
of whom it had been said, It is through Isaac that your posterity will be traced.