Sarah, the wife of the Patriarch Abraham, banishes one of her husband's concubines from her home, a woman called Hagar. Hagar is the mother of Ishmael, who signifies the force of negativity. The banishment of Hagar pertains to the removal of man's desire to receive for the self alone.
The first step in transformation involves a recognition and admittance of our self-indulgent desires. This self-acknowledgment is 90% of the battle. The Light of the Creator is then free to enter and eradicate the dark recesses of our nature. Towards that end, this passage arouses self-awareness, thus banishing our own Evil Inclinations and negative attributes from our character.