'Swear' in the Bible

Jonathan caused David to swear again, for the love that he had to him; for he loved him as he loved his own soul.

Swear now therefore to me by Yahweh, that you will not cut off my seed after me, and that you will not destroy my name out of my father's house."

David said to him, "Will you bring me down to this troop?" He said, "Swear to me by God that you will neither kill me, nor deliver me up into the hands of my master, and I will bring you down to this troop."