Standing before the gathered nation, King David offers a public declaration of thanksgiving to God. The people have just offered generous, voluntary contributions for the construction of the Temple, and the king brings everyone together to publicly acknowledge their open-hearted giving [רש"י].
In his praise, David specifically invokes God as the God of "our father Israel." This is not a general reference to the nation, but a direct mention of the patriarch Jacob, who was given the name Israel [רש"י, מצודת דוד, רד"ק]. There are two primary reasons why David singles out Jacob rather than Abraham or Isaac. First, the context of the gathering revolves around donations. Jacob was the very first person to make a vow and set aside a formal contribution to God. Because the current celebration is the direct result of the people's voluntary gifts for the Temple, David connects their actions to the patriarch who established this practice of giving for all future generations [רש"י, מצודת דוד, רד"ק].
The second reason relates to the physical location of the Temple itself. After his dream of the ladder at Mount Moriah, Jacob was the first to declare that specific site to be the house of God. As David finalizes the preparations to build that exact house, it is fitting that he praises God, who originally revealed the Temple's location and the gate of heaven to Jacob [רד"ק, מלבי"ם].
David's praise extends into eternity, offering a blessing that bridges this world and the world to come [מצודת דוד]. This expression of endless time [ביאור שטיינזלץ] eventually became the standard formula used for blessings within the Temple, carrying a deeper hint toward the eternal survival of the people of Israel [רלב"ג]. From a broader historical perspective, David shapes this eternal blessing to correct a past shortcoming. Generations earlier, Jethro—a single convert—blessed God for saving the Israelites. This created a subtle sense of embarrassment for the nation, as an outsider had offered a praise they had not fully expressed themselves. To repair this historical slight, David deliberately crafts his public praise to be grander and more everlasting than Jethro's, ensuring the nation's gratitude to God echoes forever [רש"י].