Of this manner of feeling speaketh the prophet Jeremy thus: And there was made in my heart as a fire boiling, and shut up in my bones, and I fainted, not able to bear it; which words may be understood thus: The love and feeling of God was made in my heart, not fire, but as boiling or burning fire; for as material fire burneth and wasteth all bodily things where it cometh, right so doth spiritual fire (as is the love of God) burneth and wasteth all fleshly loves and likings in a man’s soul. (John Climacus)

A fire boiling also warms and, as a steam engine, can empower mighty acts.

Jeremy (Jeremiah) was young and could not speak. He was also afraid.

God promised, "I am with you to deliver you."(Jeremiah 1:8) Yet Jeremiah was ignored, derided, and threatened.

Jeremiah tried to hold back. "I will not make mention of Him, nor speak anymore of His name."

"But His word was in my heart like a burning fire shut up in my bones, I was weary of holding it back, and I could not." (Jeremiah 20:9)