Jamieson, Fausset and Brown on Isaiah 48:10

10. (See on Is 1:25).

with silver--rather, "for silver." I sought by affliction to purify thee, but thou wast not as silver obtained by melting, but as dross [Gesenius]. Thy repentance is not complete: thou art not yet as refined silver. Rosenmuller explains, "not as silver," not with the intense heat needed to melt silver (it being harder to melt than gold), that is, not with the most extreme severity. The former view is better (Is 1:25; 42:25; Eze 22:18-20, 22).

chosen--or else [Lowth], tried ... proved: according to Gesenius, literally, "to rub with the touchstone," or to cut in pieces so as to examine (Zec 13:9; Mal 3:3; 1Pe 1:7).