We use to sing the old kid's chorus Father Abraham with all the motions and sometimes not quite understand the significance that Abraham is the model in the Bible for faith.  Paul used Abraham to appeal to both the Judaizers and the Christians who were being bewitched by adding works to salvation.  The appeal being that salvation in Scripture has always been through faith, the intent is that salvation is by grace through faith in Christ alone.  Paul reminds us that we are all under the curse and have fallen short of God's glory and that Christ became a curse for us on the cross by paying the penalty for our sin. 

Primary Scripture: Galatians 3:6-14