Jeremiah 20:9 says God's word became like what, shut up in his bones?

Answer: A burning fire

When Jeremiah tried to stop speaking, God's message became "a fire burning in my heart, shut up in my bones."

“If I say, “I will not mention Him or speak any more in His name,” His message becomes a fire burning in my heart, shut up in my bones, and I become weary of holding it in, and I cannot prevail.”— Jeremiah 20:9 (BSB)