John Gill Bible Commentary

And David said unto him, thy blood be upon thy head,.... The blood that he had shed, let him suffer for it; for as he had shed blood, his blood ought to be shed, according to the law of God; and for proof of this, that he had so done, he appeals to his own confession: for thy mouth hath testified against thee, saying, I have slain the Lord's anointed; and what might serve to confirm the truth of what he had said were the crown and bracelet which he brought along with him; and besides he was an Amalekite, of a nation that was devoted to destruction; and, as Abarbinel thinks, David might suppose that he killed Saul to take vengeance on him for what he had done to their nation; but, after all, both he and Maimonides (n) allow the punishment of him was not strictly according to law, but was a temporary decree, an extraordinary case, and an act of royal authority; for in common cases a man was not to be condemned and put to death upon his own confession, since it is possible he may not be in his right mind (o); but David chose to exercise severity in this case, partly to show his respect to Saul, and to ingratiate himself into the favour of his friends, and partly to deter men from attempting to assassinate princes, who himself was now about to ascend the throne. (n) Hilchot Sanhedrin, c. 18. sect. 6. (o) T. Bab. Yehamot, fol. 25. 2. Maimon. ibid.