Answer: They believe Moses and Jesus are Isaac's descendants
Explanation: Regarding the final prophet, Jews and Christians have different views, for Christians the final prophet is John the Baptist and after him no more prophets, while for Jews the prophets are closed with the Old Testament.
The Old Testament was written by many prophets and kings, and the first books of the Old Testament were written by Moses, who lived centuries after Isaac, so that Isaac did not write the Old Testament.
Isaac was the second son of Abraham, and he was the ancestor of all Jews, therefore Moses and Christ, who was born a Jew. Isaac had two sons, of whom Jacob, the second son, had twelve sons, of whom there are twelve tribes of Israel. Isaac as destined for the blessing from which the chosen people will descend is the ancestor of all Jews, taught by his father Abraham to believe in one God, which is the faith of the Jews. Christians who respect the Old Testament also consider themselves to be the heirs of Abraham's monotheism, which through Isaac was passed on to a chosen people, and Christ completed his mission, fulfilling the Old Testament and breathed a living faith, Christianity.
The first son of Abraham, Ismail, from whom the Arabs came, that is, the Muslims is the one who survived the desert thanks to the help of God. He and his mother were expelled from Abraham's settlement. Abraham had a wife Sarah with whom he got Isaac, but with his handmaiden Hagar he got Ismail (Ishmael), first son. When Isaac was determined to receive the blessing as the ancestor of the holy people according to God’s promise, at the urging of Abraham’s wife Sarah, Hagar and Ismail were banished and wandered through the desert. Ismail was almost dead, when God, through His angel, made the source of water flow in the middle of desert, thus saving Ismail.