Romans 4
23 Now it was not written for his sake alone that it was imputed to him, 24 but also for us. It shall be imputed to us who believe in Him who raised up Jesus our Lord from the dead, 25 who was delivered up because of our offenses, and was raised because of our justification.

The promises are NOT just for Abraham.
The promises of Abraham are also for us. The righteousness given to Abraham is also for us.
We are the children of the King, if we choose to be adopted.