1 Samuel 20:16

So Jonathan made [a covenant] with the house of David,.... Not with David himself only, which was now renewed, but with his family also:

[saying], let the Lord even require [it] at the hand of David's enemies; take vengeance on Jonathan, or on any of his posterity, should they break this covenant, by showing themselves enemies to David, and his crown; and, on the other hand, also on David, and his posterity, should they not show kindness to Jonathan and his seed, according to the tenor of this covenant.