ABC:Hebrews 11

Verse 17
The ReasonProject lists the following as a Bible contradiction with the headline "How many sons did Abraham have?"

Hebrews 11:17 By faith Abraham, when he was tried, offered up Isaac: and he that had received the promises offered up his only begotten son,

James 2:21 Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar?

Genesis 22:2 And he said, Take now thy son, thine only son Isaac, whom thou lovest, and get thee into the land of Moriah; and offer him there for a burnt offering upon one of the mountains which I will tell thee of.

Genesis 16:15 And Hagar bare Abram a son: and Abram called his son's name, which Hagar bare, Ishmael.

Genesis 21:2 For Sarah conceived, and bare Abraham a son in his old age, at the set time of which God had spoken to him. 3 And Abraham called the name of his son that was born unto him, whom Sarah bare to him, Isaac.

Genesis 25:1 Then again Abraham took a wife, and her name was Keturah. 2 And she bare him Zimran, and Jokshan, and Medan, and Midian, and Ishbak, and Shuah.

Genesis 4:22 And Zillah, she also bare Tubalcain, an instructer of every artificer in brass and iron: and the sister of Tubalcain was Naamah.

It is very odd first of all that Genesis 4:22 is included here as a contradiction, I can only assume the chart designer made a typo here as the passage is entirely unrelated. They must have intended another passage but I can't figure out which one.

Regardless, the usage of the word "son" each time was in reference to an heir. This is apparent throughout both the Old and New Testaments. Sarah, because she was originally infertile, made the somewhat ill-advised decision to ask her maid to bear Abraham's children, which she quickly recognized had been a mistake afterward. (Genesis 16:1-6) Abraham had multiple children, but only one he considered "son" in the sense of being an heir. The other sons of Abraham were not considered sons but servants. (Galatians 4:30, Genesis 21:10) Thus, Abraham sent the illegitimate children away with gifts but the overall inheritance went to Isaac alone. (Genesis 25:5-6, 24:36)

Genesis 21:9 And Sarah saw the son of Hagar the Egyptian, which she had born unto Abraham, mocking. 10 Wherefore she said unto Abraham, Cast out this bondwoman and her son: for the son of this bondwoman shall not be heir with my son, even with Isaac.

Genesis 25:5 And Abraham gave all that he had unto Isaac. 6 But unto the sons of the concubines, which Abraham had, Abraham gave gifts, and sent them away from Isaac his son, while he yet lived, eastward, unto the east country.

Galatians 4:1 Now I say, That the heir, as long as he is a child, differeth nothing from a servant, though he be lord of all;

Galatians 4:7 Wherefore thou art no more a servant, but a son; and if a son, then an heir of God through Christ.

Galatians 4:30 Nevertheless what saith the scripture? Cast out the bondwoman and her son: for the son of the bondwoman shall not be heir with the son of the freewoman.

Genesis 24:36 And Sarah my master's wife bare a son to my master when she was old: and unto him hath he given all that he hath.

It should also be pointed out that James does not say Abraham had only one son, and the book of Hebrews uses the phrase "only begotten" (Greek word monogenes ) to reference inheritance specifically.

As for Genesis 22:2, at the time Abraham had only two children, Isaac and Ishmael, and Ishmael had been sent away with Hagar for mocking Isaac (Genesis 21:9-21), effectively disinherited. Thus in Genesis 22 God referred to Abraham having only one son, given the disassociation of the other, and the fact that Isaac alone was considered an heir, the other a servant. Paul in Galatians 4 points to all of this, drawing a distinction between two covenants, the Law and that of faith, as symbolized by Ishmael and Isaac respectively.