Genesis 21:10,11

Gen. 21:10, 11, "Wherefore she said unto Abraham, Cast out this bond-woman and her son; for the son of this bond-woman shall not be heir with my son, even with Isaac." The son of the bond-woman is men's own righteousness; which is the son of the first covenant, given at mount Sinai, which is Hagar; and Isaac, the son of the free-woman, is Christ, as applied to the soul by faith: he is the child of promise, and the son of the free-woman: at least this is part of the signification. It is Sarah, the mother of Isaac, that urges the casting out of the bond-woman; so it is the church in its ministry and ordinances, which is the mother of Christ in the souls of believers, that urges the casting out our own legal righteousness. It is Christ that is the heir of the blessings of the covenant; it is by his merits only that we have a right or title to those blessings; we must cast out our own righteousness, and not have any manner of regard to that, as though that had a right, or as though a right came by that. ["And the thing was very grievous in Abraham's sight, because of his son."] This signifies how very hard and grievous it seems to persons wholly to cast out their own righteousness, the son of the legal covenant from mount Sinai, because they are our own works, our own offspring, that are dear to us, as Ishmael was to his father Abraham.

Gen. 22