11:17 only begotten son. Isaac was not really Abraham’s only begotten son, for there was Ishmael, but he was counted by God as such, since Ishmael was begotten outside the promises of God, due to a lapse of faith for a time by Sarah and Abraham. The use of the term here stresses the fact that Abraham’s offer of Isaac can be taken as a thrilling type of God’s offering His only begotten Son. See notes on Genesis 22:1-18.
11:18 it was said. This passage is quoted from Genesis 21:12.
11:19 able to raise him up. Abraham had assured his servants that he and Isaac would return (Genesis 22:5), even though he fully intended to slay Isaac in obedience to God, simply because he believed God. Thus, even in a time when no one had ever been raised from the dead, Abraham believed God would raise Isaac up in order to keep His promise. Such was the faith of Abraham!