Therefore thus saith the LORD of hosts, Behold, I will melt them, and try them; for how shall I do for the daughter of my people?
I will melt them and try them - by sending calamities on them. The image is taken from melting metals in order to purge them of their dross (cf. Jeremiah 6:29; Isaiah 1:25; Malachi 3:3, "He shall sit as a refiner and purifier of silver; and He shall purify the sons of Levi, and purge them as gold and silver, that they may offer unto the Lord an offering in righteousness").
For how shall I do - `what else can I do for the sake of the daughter of my people?' (Maurer.)