Search and Known # 3: How many sons did Abraham have?

Image:  Pedro Orrente's "The Sacrifice of Isaac" (c. 1616)

Ethan McG. has posted Searched and Known # 3, an ongoing apologetics series in which we respond to various supposed contradictions in the Bible noted in the Skeptic's Annotated Bible.

This episode responds to the challenge; How many sons did Abraham have?  The apparent contradiction:  Genesis 22:2, 12, 16 and Hebrews 11:17 describe Isaac as Abraham's only son, but other passages say he had more than one son.  He had Ishmael by Hagar, Sarah's handmaid (Gen 16:15) and he had six sons by Keturah (Gen 25:1-2).  So, Abraham had eight sons and not one.

The response:  The Bible can refer to Isaac as Abraham's only son, because he was Abraham's only son by Sarah, the only son of promise through whom the covenant would continue and through whom the promise to Abraham would be fulfilled (Gen 3:1-3).  It is from the line of Isaac that Jesus would come.  Paul can refer to Jesus as "the seed of Abraham" (Gal 3:16) and describe all believers, whether Jew or Gentile, as the spiritual seed of Abraham (Gal 3:29).

JTR