In whose house did the ark stay for three months, bringing God's blessing?

Answer: Obed-edom the Gittite

After Uzzah died, David left the ark with Obed-edom. The LORD blessed his household, so David brought the ark up with rejoicing.

“So he was unwilling to move the ark of the LORD to the City of David; instead, he took it aside to the house of Obed-edom the Gittite.”— 2 Samuel 6:10 (BSB)