But the king shall rejoice in God,.... Not Saul, as R. Obadiah; as if David wished him well, and that he might have reason to rejoice in God, though he sought his hurt; which sense is rejected by Abea Ezra: but either David, who speaks of himself as king, being anointed by Samuel, and who, upon the death of Saul, was so in fact; and who rejoiced, not merely at the destruction of his enemies, for he lamented the death of Saul, 2Sa 1:17; but in God, in his grace and goodness to him, and in his power and justice shown in the vengeance taken on them.
Or rather, the King Messiah, who rejoiced in God because of the good of his people, their conversion and salvation, and their deliverance from their enemies, Ps 21:1;everyone that sweareth by him shall glory; not by David, though such a form of swearing was used; see 2Sa 15:21; or, "to him": and so describes his faithful subjects swearing allegiance to him: but rather by the Lord, in whom the king should rejoice; and designs the worshippers of him; swearing by him being sometimes put for the whole worship and service of God, De 6:13.
The Heathens used to swear by their deities, and their chief was called Jupiter Horcius, because he presided over oaths . Or else that the King Christ should rejoice in God; and intends such as believe in him and confess him; see Isa 45:23, compared with Ro 14:11.
And every such an one will glory, not in themselves, nor in anything of theirs, but in Christ, in his grace and righteousness, and in what he is unto them;but the mouth of them that speak lies shall be stopped; such as Saul's courtiers, who invented and spread lies of David; but now upon the death of Saul, and David's advancement to the throne, would be silent; their mouths being stopped either by death, or through fear: and so all the followers of antichrist, that make and believe a lie, will have their mouths stopped, when cast into the lake of fire, Re 21:8.
Euripidis Medea, v. 170. Vid. Alex. ab Alex. Genial. Dier. l. 5. c. 10.