Genesis 21:31 New English Translation

³¹That is why he named that place^[a] Beer Sheba,^[b] because the two of them swore an oath^[c] there.

Genesis 21:31 tn Heb “that is why he called that place.” Some translations render this as an impersonal passive, “that is why that place was called.”
Genesis 21:31 sn The name Beer Sheba (בְּאֵר שָׁבַע, b^eʾer shavaʿ) means “well of the oath” or “well of the seven.” Both the verb “to swear” and the number “seven” have been used throughout the account. Now they are drawn in as part of the explanation of the significance of the name.
Genesis 21:31 sn The verb forms a wordplay with the name Beer Sheba.

New English Translation (NET)