Genesis 26:33
And he called it Shebah: therefore the name of the city is Beer–sheba unto this day.
Cross-reference
Genesis 26:28
Historical context
Genesis 26:28 describes the oath Isaac and Abimelech swore — the name Shibah here directly commemorates that sevenfold agreement.
Genesis 21:31
Historical context
Genesis 21:31 records Abraham naming the same place Beersheba after his oath with Abimelech — Isaac here echoes his father's naming of this site.
Genesis 21:33
Parallel
Genesis 21:33 records Abraham planting a tamarisk and worshiping at Beersheba — Isaac's naming continues his father's legacy at this sacred place.