Commentary for I Samuel 20:42

וַיֹּ֧אמֶר יְהוֹנָתָ֛ן לְדָוִ֖ד לֵ֣ךְ לְשָׁל֑וֹם אֲשֶׁר֩ נִשְׁבַּ֨עְנוּ שְׁנֵ֜ינוּ אֲנַ֗חְנוּ בְּשֵׁ֤ם יְהוָה֙ לֵאמֹ֔ר יְהוָ֞ה יִֽהְיֶ֣ה ׀ בֵּינִ֣י וּבֵינֶ֗ךָ וּבֵ֥ין זַרְעִ֛י וּבֵ֥ין זַרְעֲךָ֖ עַד־עוֹלָֽם׃ (פ)

And Jonathan said to David: ‘Go in peace, forasmuch as we have sworn both of us in the name of the LORD, saying: The LORD shall be between me and thee, and Between my seed and thy seed, for ever.’

Rashi on I Samuel