Genesis 21
The new light in Christ always reveals the nature of the old life, and the old life must be purged out. The flesh attacks the spirit and persecutes the godly. Sarah spoke the first words ever recorded in the Bible preaching the divine truth of expelling the carnal nature of life, and purging out the old leaven, she said to him in Genesis 21:10: Cast out this bondwoman and her son, for the son of the bond-woman should not be heir with my son, even with Isaac.