Galatians 3:16
(Now the promises were given to Abraham and to his seed. God did not say 'and to seeds,' as if speaking of many, but 'and to your seed,' since He spoke of only one--and this is Christ.)
Romans 9:8
In other words, it is not the children by natural descent who count as God's children, but the children made such by the promise are regarded as Abraham's posterity.
Galatians 4:28
But you, brethren, like Isaac, are children born in fulfilment of a promise.
Hebrews 11:13
All these died in the possession of faith. They had not received the promised blessings, but had seen them from a distance and had greeted them, and had acknowledged themselves to be foreigners and strangers here on earth;