1 Samuel 20:16

The covenant which before was personal, he now extends to the whole house of David, expecting a reciprocal enlargement of it on David's side, which doubtless he obtained. Let the Lord even require it at the hand of David's enemies; if either I or any of my house shall break this covenant, and shall prove enemies to David, or to his house, let the Lord, the witness of this covenant, severely punish the violators of it, whoever they are. Others thus, Let the Lord require and punish the breach of this covenant in David, if he break it. But because it was ominous and reproachful to suppose such a thing of David, by a figure called euphemismus, he names David's enemies for David; as they also expound 1 Samuel 25:22. But the former sense seems more probable, because this verse contains only Jonathan's stipulation or covenant with David and his house, which being expressed in the former part of it, is in this latter part confirmed by the usual form of imprecation; and the restipulation or covenant of David to Jonathan and his house is mentioned in the next verse. Yet may that other sense stand well enough; taking these words for Jonathan's adjuration of David to be kind to him, confirmed with an imprecation in case he do otherwise; as if he should say, I adjure thee, as thou hopest to escape such a mischief, (which I had rather might befall thine enemies than thee,) that thou deal not so ungratefully with me or my house: which adjuration of Jonathan David seconds by an oath in the next verse, at the request of Jonathan.