We will keep establishing this pattern of the “bone day,” and the next one is in Genesis 17:
This was another highly significant day in God’s outworking, and God underscores it by mentioning the “very same day” twice. This one is harder to nail down, but we can begin with the fact that Genesis 17 does not stand on its own. There was already a history. There were events and divine pronouncements that came before and resulted in this “bone day” and proved God’s faithfulness. Perhaps it was the covenant in Genesis 15.
Another possibility—and, I believe, a better one—goes back even farther, to the first time God appeared to Abram when he got to Canaan. On that occasion, God promised, “To your descendants I will give this land” (Genesis 12:7). It was a promise of both inheritance as well as descendants. There is an echo of that promise on this esem day in verse 8 here, where God says,
So, when Abram got to the land, God said, “To your descendants I will give this land,” and on this esem day, God confirms it. His words change from “I will give” to “I give” as He faithfully fulfilled His promise from decades before.
What God did here was add circumcision as a requirement and as the sign that those bearing this mark had made the covenant at the same time with Abraham. (I believe that this term "selfsame day" appears something like fourteen times in the Bible.)
