This verse, 1 Chronicles 17:15, acts as a summary statement, essentially confirming that Nathan the prophet delivered the entirety of God's message, both in spoken words and in the visual representation (the vision), to King David. Let's break it down:

"According to all these words...": This refers to the specific verbal message God gave to Nathan. This message would have included promises, prophecies, and perhaps warnings. It encompassed the details of what God wanted David to know.

"...and according to all this vision...": This indicates that Nathan also received a visual representation, a "vision," from God. This vision would have been a symbolic or illustrative portrayal of God's message, perhaps emphasizing specific aspects or conveying a deeper understanding. The vision complements and reinforces the spoken words.

"...so Nathan spoke to David.": This is the key point. It emphasizes Nathan's faithfulness and accuracy in relaying the divine communication to David. He didn't omit anything, add anything, or change anything. He delivered the message exactly as he received it, both the words and the vision.

In essence, the verse highlights Nathan's role as a trustworthy and accurate messenger of God's will. It confirms the authenticity and completeness of the prophecy delivered to David, setting the stage for David's response and actions based on this divine communication.

The significance lies in:

Divine Authority: The verse emphasizes that the message comes directly from God, not from Nathan's own imagination or interpretation.
Prophetic Accuracy: It highlights the importance of prophets conveying God's message truthfully and completely.
Foundation for Action: It provides the context for David's subsequent actions, which are based on the belief that he has received a clear and accurate message from God.

In short, 1 Chronicles 17:15 is a crucial verse that affirms the divine origin and accurate transmission of a pivotal prophecy to King David.