Now it came to pass when the king was dwelling in his house, and the Lord had given him rest from all his enemies all around, that the king said to Nathan the prophet, “See now, I dwell in a house of cedar, but the ark of God dwells inside tent curtains.”
Then Nathan said to the king, “Go, do all that is in your heart, for the Lord is with you.”
But it happened that night that the word of the Lord came to Nathan, saying, “Go and tell My servant David, ‘Thus says the Lord: “Would you build a house for Me to dwell in?” 2 Samuel 7:1-5

David had good and honorable intentions to build a house of worship for God. The idea seemed a good one to the king’s spiritual advisor, Nathan.
It did not seem necessary to pray about the plans – it was to honor God!
It did not take long for God to speak up and put a halt to the whole thing.
God forbids David from completing the project but promises his son will do it.

Jesus said in Luke 14:28-30, “For which of you, intending to build a tower, does not sit down first and count the cost, whether he has enough to finish it — lest, after he has laid the foundation, and is not able to finish, all who see it begin to mock him, saying, ‘This man began to build and was not able to finish.’”

Always include prayer as part of “counting the cost” in any plans you make – even if it seems a good honorable idea. Meaning no disrespect, had David and Nathan prayed first they would not get their hopes up only to have them squashed.
Even stepping out on blind faith requires prayer.