Conscience is unnatural, the consequence of the slave's manipulation designed to immobilize the strong. Nietzsche writes of the genius of the Jews and Judaism. Jews were born slaves and they succeeded in changing the meaning of good and bad. The slave insists that human beings are to live according to God's nature, patient, compassionate, forgiving and loving. Judaism, Nietzsche maintained, is responsible for the cultural revolution that stems from the anger of impotence.
Master morality says yes to nature, slave morality says no.
Morality is a subjective matter and depends upon strength, power and status. If you are strong and well positioned in society, your philosophy will favor Nietzsche and Machievelli and before them Callicles and Thrasymachus. Only the Jews dared to suggest that which is counter to master morality. Nietzsche maintained that books of law and ethics are the works of the establishment and reflect the interests of the strong and the powerful. The Bible appears as the notable exception.