פירוש על שמואל ב 21:7

The king had pity. He prayed for pity on Mephivoshes that the Ark should not detain him; because Dovid had them [Shaul's children] pass before the Ark, whomever the Ark detained, was put to death.¹⁵i.e., was handed over to the Givonim who subsequently put them to death. Yevomos 79a.