Who declared, "As for me and my house, we will serve the LORD"?

Answer: Joshua

Joshua told Israel to choose whom they would serve, then declared, "As for me and my house, we will serve the LORD!"

“But if it is unpleasing in your sight to serve the LORD, then choose for yourselves this day whom you will serve, whether the gods your fathers served beyond the Euphrates, or the gods of the Amorites in whose land you are living. As for me and my house, we will serve the LORD!””— Joshua 24:15 (BSB)