'Promise' in the Bible

For the promise to Abraham or to his descendants that he would inherit the world was not fulfilled through the law, but through the righteousness that comes by faith.

For if they become heirs by the law, faith is empty and the promise is nullified.

For this reason it is by faith so that it may be by grace, with the result that the promise may be certain to all the descendants -- not only to those who are under the law, but also to those who have the faith of Abraham, who is the father of us all

He did not waver in unbelief about the promise of God but was strengthened in faith, giving glory to God.

This means it is not the children of the flesh who are the children of God; rather, the children of promise are counted as descendants.

For this is what the promise declared: "About a year from now I will return and Sarah will have a son."