But the king shall rejoice - David shall come to the kingdom according to the promise of God. Or, if it refer to the captivity, the blood royal shall be preserved in and by Zerubbabel till the Messiah come, who shall be David's spiritual successor in the kingdom for ever.

That sweareth by him - It was customary to swear by the life of the king. The Egyptians swore by the life of Pharaoh; and Joseph conforms to this custom, as may be seen in the book of Genesis, Genesis 42:15, Genesis 42:16. See also 1 Samuel 1:26 : 1 Samuel 17:55, and Judith 11:7. But here it may refer to God. He is The King, and swearing by his name signifies binding themselves by his authority, acknowledging his supremacy, and devoting themselves to his glory and service alone.

The Chaldee has: "And the King shall rejoice במימר אלהא bemeymar Eloha, in the Word of God;" or, in the Word God; Meymar, Word, being taken here substantially, as in many other places, by the Targumist.

The mouth of them that speak lies - The mouth of those who acknowledge lying vanities, that worship false gods, shall be stopped. All false religions shall be destroyed by the prevalence of the truth. For he, Christ, shall reign till all his enemies are put under his feet. "Thy kingdom come, and hell's o'erpower: and to thy scepter all subdue." Amen and Amen.

But, David shall come to the kingdom according to the promise of God

The king

Psalm 2:6 Yet have I set my king on my holy hill of Zion.

Psalm 21:1 The king shall joy in your strength, O LORD; and in your salvation how greatly shall he rejoice!

1 Samuel 23:17 And he said to him, Fear not: for the hand of Saul my father shall not find you; and you shall be king over Israel...

1 Samuel 24:20 And now, behold, I know well that you shall surely be king, and that the kingdom of Israel shall be established in your hand.

sweareth

Deuteronomy 6:13 You shall fear the LORD your God, and serve him, and shall swear by his name.

Isaiah 19:18 In that day shall five cities in the land of Egypt speak the language of Canaan, and swear to the LORD of hosts; one shall be called...

Isaiah 45:23 I have sworn by myself, the word is gone out of my mouth in righteousness, and shall not return, That to me every knee shall bow...

Isaiah 65:16 That he who blesses himself in the earth shall bless himself in the God of truth...

Zephaniah 1:5 And them that worship the host of heaven on the housetops; and them that worship and that swear by the LORD, and that swear by Malcham;

Hebrews 6:13 For when God made promise to Abraham, because he could swear by no greater, he swore by himself,

the mouth

Psalm 31:18 Let the lying lips be put to silence; which speak grievous things proudly and contemptuously against the righteous.

Romans 3:19 Now we know that what things soever the law said, it said to them who are under the law: that every mouth may be stopped...

Titus 1:10,11 For there are many unruly and vain talkers and deceivers, specially they of the circumcision...

Out of the Deep of Death.
My heart is disquieted within me, and the fear of death has fallen upon me.--Ps. iv. 4. My flesh and my heart faileth, but God is the strength of my heart.--Ps. lxiii. 25. Yea though I walk through the valley of the shadow of death, I will fear no evil, for Thou art with me.--Ps. xxiii. 4. Thou hast delivered my soul from death, mine eyes from tears, and my feet from falling.--Ps. cxvi. 8. What will become of us after we die? What will the next world be like? What is heaven like? Shall I be able …
Charles Kingsley—Out of the Deep

Covenanting Confers Obligation.
As it has been shown that all duty, and that alone, ought to be vowed to God in covenant, it is manifest that what is lawfully engaged to in swearing by the name of God is enjoined in the moral law, and, because of the authority of that law, ought to be performed as a duty. But it is now to be proved that what is promised to God by vow or oath, ought to be performed also because of the act of Covenanting. The performance of that exercise is commanded, and the same law which enjoins that the duties …
John Cunningham—The Ordinance of Covenanting

The Marks of the New Birth
"So is every one that is born of the Spirit." John 3:8. 1. How is every one that is "born of the Spirit," -- that is, born again, -- born of God? What is meant by the being born again, the being born of God, or being born of the Spirit? What is implied in the being a son or a child of God, or having the Spirit of adoption? That these privileges, by the free mercy of God, are ordinarily annexed to baptism (which is thence termed by our Lord in a preceding verse, the being "born of water and of the …
John Wesley—Sermons on Several Occasions