'Swear' in the Bible

and Jonathan addeth to cause David to swear, because he loveth him, for with the love of his own soul he hath loved him.

and, now, swear to me by Jehovah -- thou dost not cut off my seed after me, nor dost thou destroy my name from the house of my father.'

And David saith unto him, 'Dost thou bring me down unto this troop?' and he saith, 'Swear to me by God -- thou dost not put me to death, nor dost thou shut me up into the hand of my lord -- and I bring thee down unto this troop.'