In the vessels of psalms - Thy truth, O God - David refers to the various musical instruments he will use to glorify the truth of God. Ultimately, the vessels of the psalm signify the Christians, whose spirits, according to Eusebius, have been harmonized and joined together, allowing David to continuously offer praise to God through them. The same verb, "I will confess," appears here, indicating that it would have been fitting to express it in the dative as “to Thy truth.” However, he uses the accusative, stating, "I will confess Thy truth, O Lord," meaning that God is the true deity, not only in His nature but also in His promises and words.
Athanasius notes that through confession, I shall be empowered to be considered a vessel of song. Just as one may be called a vessel of election in Scripture, it follows that one can also be labeled a vessel of song. Isychius remarks that my confession will not stem from mere instruments of sound but from a pure heart and a holy tongue—one that speaks nothing contrary to holiness—for these are genuinely and righteously recognized as the vessels of the psalm.
"I will sing unto Thee in psalteries, O Holy One of Israel" clarifies the earlier remarks, for the vessel of song also includes the psalter, through which David highlighted the other musical instruments. By psaltery, he denotes the royal instrument on which he sang the psalms, as mentioned in the preface of this book. Similarly, these instruments can also apply to us; the vessels of the psalm can refer to the mouth, the lips, the tongue, and all that serves as conduits for human voice, while the psaltery symbolizes the soul. The Holy One of Israel represents the God who sanctifies His people.
Both God and humanity are referred to as Holy—God by nature and man by grace, or communion. The truth of this is affirmed by the apostle Paul, who writes of Christ, "Who was made unto us wisdom from God, righteousness, and sanctification, and redemption," meaning that He is wisdom to the taught, righteousness to the justified, and sanctification and deliverance to those who are made holy and freed.