The story of Abram has already had several interactions between Abram and his Creator.
Now comes another instance where the story is altered by a direct communication with God.
Abram has already gotten instructions to move to Caanan, and already been given a list of tribal lands that will belong to his descendants. God repeats this promise, but merely names the land as Caanan this time.
Abram is given a new name: Abraham. His wife Sarai is also given a new name: Sarah. The promise of descendants is repeated, with a special mention of Sarah as the mother of those descendants. The name of Isaac is mentioned for the promised son, and a date is given.
A special sign of this covenant is given, the covenant of circumcision. All the men in Abraham's household are instructed to go through this action. The act is a sign, in the flesh of men from the culture, that they are different. Yet it is a sign that is not obvious to most outside observers.
This formal statement of a promise from God and a covenant of circumcision is separated from a special visit, as told in the next section of the story*.
In the next section, the story-telling style looks more like the story of Abraham's interactions with his neighbors. He's sitting in his tent, and sees travelers. Then he greets those travelers with courtesy expected among nomadic peoples in arid climates.
One of the men asks about Sarah, and then re-iterates the promise given by God to Abraham in the previous story. "By this time next year, she will have a son."
Sarah, overhearing the conversation, laughs. The men (one of whom is suddenly named as the Creator, or a special incarnation of His presence), asks about the laughter, and repeats the promise about the birth a son within a year.
Here we have two separate stories that promise the birth of Isaac within a specified period of time. One is related to the covenant of circumcision, the other is related to the Creator somehow manifesting in a form that allows face-to-face conversation with Abraham.
The covenant of circumcision seems an odd one. It is a sign, but a sign that is not often made visible to outsiders. It is a sign that is ever-present, yet not often shown. It is more to remind the bearer of the sign, than to remind others. It is also a change that is impossible to reverse.
This seems part of the personal nature of the interaction of Abraham and his people with God. It is more important that the bearers of this sign know that they wear it, than that others know. And it reminds them that God sees things that can be hidden from other men.
*This second story addresses the Creator by a different name. Yet the promises given are similar, even though the interaction is vastly different.
Was this an artifact of different branches of the Abrahamic family remembering the events in different ways, and underlining different details of the events?
Were these two separate encounters with the Creator, or one?