The Pharisees placed their security in their heritage and their salvation by works. As descendants of Abraham, the Pharisees felt safe and secure.
“They (Pharisees) answered Him (Jesus), ‘We are Abraham’s descendants, and have never been in bondage to anyone’. How can You say, ‘You will be made free’?” John 8:33
Jesus acknowledged their claim, but set them straight in their thinking.
“I know that you are Abraham’s descendants, but you seek to kill Me, because My word has no place in you. I speak what I have seen with My Father, and you do what you have seen with your father.” John 8:37-38
The Pharisees persisted in the argument that Abraham was their father and therefore they were safe and beyond reproach. They advanced the argument by claiming that God Himself was their Father.
“Jesus said to them, ‘If God were your Father, you would love Me, for I proceeded forth and came from God…Why do you not understand My speech?…You are of your father the devil, and the desires of your father you want to do…’.” John 8:42-44
There are yet today many modern day Pharisees who still believe that being the descendants of Abraham is sufficient for salvation. Paul confronted that same argument as he wrote to the Christians in Rome.
“What then shall we say that Abraham our father has found according to the flesh? For if Abraham was justified by works, he has something to boast about…For what does the Scripture say? Abraham believed God, and it was accounted to him for righteousness.” Romans 4:1-3
Abraham was indeed justified, or deemed righteous before God, but not by obeying the law (which no man could do) but rather by taking God at His word. He believed in that which God had promised even though he hadn’t seen the proof of the promise. If he had indeed fulfilled the law then he really would have had something to boast about!
The sum of the matter is that one is saved by believing the latest and final revelation of God which in this generation is Christ, the only one capable of fulfilling the complete law.
Paul then makes the issue even more clear by specifying which of Abraham’s lineage will inherit the promise of salvation. In other words, not all of Abraham’s descendants will receive the ultimate promise.
“…For they are not all Israel who are of Israel, nor are they all children because they are the seed of Abraham; but, ‘In Isaac your seed shall be called’… those who are the children of the flesh, these are not the children of God; but the children of the promise are counted as the seed.” Romans 9:6b-8
Subsequently Paul explained in more detail the difference between those born under the promise and those born under the law, or works.
“Tell me, you who desire to be under the law… Abraham had two sons; the one by a bondwoman, the other by a freewoman. But he who was of the bondwoman was born according to the flesh (law), and he of the freewoman through promise…” Galatians 4:21-23
Paul goes on to describe the two sons.
“Now we, brethren, as Isaac was, are children of promise. But, as he who was born according to the flesh (law) then persecuted him who was born according to the Spirit, even so it is now. Nevertheless what does the Scripture say? ‘Cast out the bondwoman and her son, for the son of the bondwoman shall not be heir with the son of the freewoman’. So then brethren, we are not children of the bondwoman but of the free.” Galatians 4:28-31
This extremely profound passage clarifies the teaching of the two original sons of Abraham.
“Then God said, ‘No, Sarah your wife shall bear you a son, and you shall call his name Isaac; I will establish My covenant with him for an everlasting covenant, and with his descendants after him’.” Genesis 17:19
The Pharisees of Jesus’ time apparently did not understand the Genesis account or the significance of the two brothers. Modern day Pharisees are basically the same as their first century counterparts, i.e. confidence in salvation by works.