וַיִּכְרֹ֥ת יְהוֹנָתָ֖ן עִם־בֵּ֣ית דָּוִ֑ד וּבִקֵּ֣שׁ יְהוָ֔ה מִיַּ֖ד אֹיְבֵ֥י דָוִֽד׃
So Jonathan made a covenant with the house of David: ‘The LORD even require it at the hand of David’s enemies.’
Read halakhic rulings (Jewish law) on I Samuel 20:16: and classical halakhic sources.