Jamieson, Fausset and Brown on Isaiah 1:25

25. turn ... hand--not in wrath, but in grace (Zec 13:7), "upon thee," as Is 1:26, 27 show; contrasted with the enemies, of whom He will avenge Himself (Is 1:24).

purely--literally, "as alkali purifies."

thy dross--not thy sins, but the sinful persons (Jr 6:29); "enemies" (Is 1:24); degenerate princes (see on Is 1:22), intermingled with the elect "remnant" of grace.

tin--Hebrew, bedil, here the alloy of lead, tin, &c., separated by smelting from the silver. The pious Bishop Bedell took his motto from this.