The idiom "the word of God came to" is used to introduce a special message from God. Alternate translation: "God gave a message to Nathan. He said, 'Go" or "God spoke this message to Nathan: 'Go" (See: [[rc://en/ta/man/translate/figs-idiom]])
This has quotations within quotations. It may be necessary to translate them as indirect quotations. Alternate translation: "saying, 'Go and tell David my servant that he will not be the one to build a house in which I will live" (See: [[rc://en/ta/man/translate/figs-quotesinquotes]] and [[rc://en/ta/man/translate/figs-quotations]])
Here "house" means a temple. In [1 Chronicles 17:10](../17/10.md) Yahweh will say that he will build a house for David. There "house" means a family. If your language has a word that can express both ideas, use it here and in 17:10.