From The Gift of the Jews by Thomas Cahill, explain the agreement ("Covenant") between Avraham (Abraham) and God (El) and its conditions.
According to Cahill, on Abraham's side of the covenant he will have a new name, changing from Avram to Avraham, which means Father of many nations. Sarai, his wife, will also receive a new name: Sara, which means Princess. Abraham will also receive a much more important gift: a child in a year's time. This is particularly important to the wheeling-dealing Abraham, because both he and Sara are very old, past the childbearing years, so both must rely on a supernatural intrusion to have any hope of conceiving.
On his side, God insists this covenant be sealed with blood through the circumcising of every male Israelite, whether the person is a slave or born an Israelite, from that time until eternity. As Cahill notes, this mark on the body of every male binds the Israelites very closely to God. Cahill writes:
"It is impossible for any man to forget his penis ... the children of Avram will be virtually unable to forget the god who never forgets them."
This personal, daily relationship turns El from the more distant "guardian angel aspect of the Sumerian patronal gods" to, quite simply, "God" with a capital G.