Question: Aaron, is isaac somehow considered the father of christianity? or at least the head of the lineage? just trying to understand the whole isaac/ishmael xtianity/islam thing. any help would be great. thanks!
Answer: Thank you for the question. I'll try to boil it down the best I can
since this is a very fundamental issue and it's often misunderstood. Unfortunately, the question doesn't lend itself to a short answer.
According to the Bible, God promised Abraham that he would have a son through his wife Sarah and that it would be through Sarah's son that all the nations of the earth would be blessed. Between the time that God made this promise to Abraham and when the promise was actually fulfilled was about 22 years. During this period of waiting, Abraham got impatient and his wife Sarah suggested that he go into their maidservant Hagar. It was the result of Abraham's union with Hagar that Ishmael was born. Ishmael was conceived through Hagar and was the firstborn, but Isaac was conceived through Sarah and became the child of promise.
Unfortunately there was friction between the two women, Sarah and Hagar, so eventually Sarah cast Hagar into the desert at
which point an angel had mercy on her and her son and promised that Ishmael would also father a great nation. Interestingly, Ishmael was actually promised a much larger piece of land than was promised Isaac. According to both Jewish, Christian, and Islamic Scriptures, Ishmael became the father of the Arab people. Isaac is the son of promise in that it was through his lineage that Jesus the Messiah was born, thus fulfilling the promise that it would be through Abraham's seed that
all the nations of the earth would be blessed.
How does this relate to Christianity and Islam? In Galatians 4:21-31, the Apostle Paul allegorizes the story of Isaac and Ishmael to make the point that those who place their faith in Christ for salvation, regardless of their physical lineage, are the true children of promise and are therefore children of Isaac. Jews that don't believe in Jesus, on the other hand, even though they are physical descendants of Isaac, spiritually speaking they are descendants of Hagar because they're trusting in the works of the law to save them. Most Christians scholars, and I agree with this interpretation, would identify Muslims as spiritual children of Ishmael because there's very little theological difference between the path of salvation in Islam
and the path of salvation in Judaism.
Two more points need to be made. In Genesis 22, there's a story where God, in order to test Abraham's faith, asked Abraham to sacrifice Isaac on an altar. Just as Abraham lifts up the knife to slay his
son, an angel intervenes, commends Abraham's faith and then directs Abraham to a ram caught in a bush to take the place of Isaac. Christians see the ram as a type of Christ in this story. Muslims actually have the same story in the Koran, but according to Islamic tradition, they believe it was Ishmael that Abraham almost sacrificed on the altar, not Isaac, although in the Koran it simply says the firstborn.
Lastly, some say that the story of Isaac and Ishmael means that Jews and Arabs will always be at war with each other. They say that Ishmael was a wild man and persecuted Isaac, therefore the Arab race will always be antagonistic towards the Jews. I strongly disagree with this interpretation. The New Testament makes it clear that Christ has broken down the wall of hostility between Jew and Gentile (Ephesians 2:14), and besides, Arabs were present at the day of Pentecost. Whether a person is Arab or Jew, it's faith in Jesus that makes a person a child of Isaac, and Jesus calls His followers to be peacemakers!
I know that's a mouthful, but it's an enormous issue. Hope this helps.