עַל־כֵּ֗ן קָרָ֛א לַמָּק֥וֹם הַה֖וּא בְּאֵ֣ר שָׁ֑בַע כִּ֛י שָׁ֥ם נִשְׁבְּע֖וּ שְׁנֵיהֶֽם׃
Wherefore that place was called Beer-sheba; because there they swore both of them.
Read kabbalistic (mystical) interpretation of Genesis 21:31: and classical mystical sources.