For thou, O God, hast heard my vows: thou hast given me the heritage of those that fear thy name.
-Ground of his confidence-namely, the prophetic Word of God (2 Samuel 7:1-29), which guarantees to him eternal dominion.
Verse 5. For thou, O God, hast heard my vows - i:e., my payers mixed with vows of thanksgiving. His prayers were what drew forth the promise of God by Nathan (2 Samuel 7:1-29; Psalms 21:2-4).
Thou hast given (me) the heritage of those that fear thy name. "The heritage" is explained in Psalms 61:6 the prolongation of the king's life, and the abiding kingdom of his posterity over Canaan, the land that belongs to the Israelites, whose feature of distinction from the Gentiles is, that they fear thy name. This gives the king confident (hope even in exile.
Verse 6. Thou wilt prolong the king's life - though now my days seem near their end. 'Thou wilt add days to the days of the king' (Isaiah 38:5; Psalms 21:4). He says "the king's" for my, because the promises belonged not merely to him as an individual, but as king and head of a royal line.
His years as many generations - literally, 'as generation and generation.' David lived in the person of his royal posterity for "many generations." But it is in Christ, the seed of David, that the promise finds its perfect fulfillment. He lives "after the power of an endless life" (Hebrews 7:16).
Verse 7. He shall abide before God forever - literally, 'he shall sit,' namely, upon the throne. Sitting is the symbol of reigning (Jeremiah 13:13). "Before God" - i:e., under His perpetually protecting grace (2 Samuel 7:29).
O prepare mercy and truth - Hebrew, 'appoint,' etc. "Mercy and truth" are God's ministers appointed by Him and sent (Psalms 43:3; Psalms 57:3) to preserve the Lord's anointed king and people.
Verse 8. So - as an acknowledgment of thy goodness.
Will I sing praise ... that I may daily perform my vows. Praise is the soul and spirit of every acceptable vow.