We have already talked about the son of flesh (Ishmael), but in this chapter we are finally introduced to the son of promise (Isaac). Remember, these two sons depict two people groups and two covenants. Ishmael represents those who seek righteousness through their own efforts and those who will not believe in Jesus. Isaac represents those who pursue righteousness through the promise of God and the means of faith and grace, those who gladly put their faith in Jesus. Paul brings this truth to greater focus in Galatians 4 when he says of Hagar and Sarah (the mothers of the two boys in question), "The women represent two covenants. One covenant is from Mount Sinai (where the Law of Moses was given) and bears children who are to be slaves: This is Hagar." And "The Jerusalem that is above (the kingdom of heaven) is free, and she is our mother." In Romans, Paul states, "It is not the children by physical descent who are God's children, but it is the children of promise who are regarded as Abraham's offspring." It would greatly benefit us if we could understand the relationship between these two sons of Abraham and how they bear on our understanding of things related to faith and salvation.

You will doubtless note in Genesis 21:9 that Ishmael (the son of flesh and of slavery) mocked Isaac (the son of promise and faith). So, it stands true today that the people who put faith in Jesus as the means of salvation are mocked by those seeking to utilize their own efforts for righteousness...