Dispensationalists claim that the promises to Abraham can only be inherited by his physical descendents. Last time, I argued from Genesis 12-17 that the promises to Abraham are inherited by his spiritual descendents, that is, those who share the faith, not necessarily the blood, of Abraham. This can be illustrated from the OT, but it is even more clear in the NT.
For instance, Paul states this very thing in Galatians 3:7,
“Therefore know that only those who are of faith are sons of Abraham.”
Paul is making a distinction among the children of Abraham. Not all of Abraham’s physical descendents will inherit the promises of Abraham. Specifically, only those who share Abraham’s faith are considered sons of Abraham.
Only those physical descendents who also have faith will receive the blessings of the covenant that God made with Abraham, as Paul states in Galatians 3:9,
“So then those who are of faith are blessed with believing Abraham.”
Thus, God’s covenant with Abraham is not an “unconditional” covenant with all of Abraham’s physical descendents. Rather, faith is the condition of inheriting the blessings. The unfaithful are cut off.
Furthermore, faithful non-physical descendents of Abraham can be grafted into the promises, as Paul states in Galatians 3:14,
“that the blessing of Abraham might come upon the Gentiles in Christ Jesus, that we might receive the promise of the Spirit through faith.”
Gentiles, who are not physically related to Abraham, can be grafted into the promises of Abraham if they are spiritually related to Abraham, that is, if they possess faith.
Therefore, in order to inherit the promises to Abraham, you must believe like Abraham (i.e., be a spiritual descendent). You don’t have to look like Abraham (i.e., be a physical descendent). As long as you possess faith, you could like Alf, and Abraham would still call you his son. Ha!