1 Samuel 20:16-17, 42

So Jonathan made a covenant with the house of David, saying, “May the LORD call David’s enemies to account.” And Jonathan had David reaffirm his oath out of love for him, because he loved him as he loved himself.

Jonathan said to David, “Go in peace, for we have sworn friendship with each other in the name of the LORD, saying, ‘The LORD is witness between you and me, and between your descendants and my descendants forever.’ ” Then David left, and Jonathan went back to the town.