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.
Nevertheless - BUT let not believers be disheartened at the prospect of persecution; for "Scripture saith," etc. Genesis 21:10; Genesis 21:12, Sarah's words confirmed by God - "Shall not be heir with my son, even with Isaac." But what was there said literally is here by inspiration applied in its allegorical import to the New Testament believer, antitypically "the son of the free woman." In John 8:35-36, Jesus refers to this.
Cast out - from the house and inheritance: literally, Ishmael; spiritually, the carnal and legalists.
Shall not be heir, х ou (G3756) mee (G3361) kleeronomeesei (G2816)] - 'must not (shall in no wise) be heir.' So Jephthah, Judges 11:2.