Cast out, &c. See the Divine interpretation. Galatians 1:3, Gal 1:6-29. Galatians 4:22-31.
with my son, &c Hebrew idiom "with my son with Isaac". Compare Numbers 12:8.
Related Commentaries of Genesis 21:10
Genesis 21:10
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.