John Wesley on Jeremiah 19:5

To burn - This and the following verse, contain another great sin of this people, with the punishment which God proportions to it. The sin in the general was idolatry, but a most barbarous species of it, mentioned also chap.7:31 32:35, where it is said, they made their sons and their daughters pass thro' the fire to Molech; the place where they did it is called Tophet, ver.19:6, of which also mention is made, Isa 30:33. Baal and Molech, signify the same thing; Baal signifies a Lord, Molech a King. Both Baal and Molech seem common names to all idols.