Albert Barnes Commentary Isaiah 1:25

"and I will turn my hand upon thee, and thoroughly purge away thy dross, and will take away all thy tin;" — Isaiah 1:25 (ASV)

And I will turn my hand upon thee - This expression is capable of two meanings. The hand may be stretched out for two purposes: either to inflict punishment or to afford help and protection. The phrase here refers clearly to the latter, to the act of redeeming and restoring His people (Isaiah 1:26–27). The idea may be expressed this way: ‘I will stretch out my hand to punish my enemies (Isaiah 1:24), and will turn my hand upon you for protection and recovery.’

Purge away - This refers to the process of smelting, or purifying metals in the fire. It means, I will remove all the dross that has accumulated (Isaiah 1:22), and will make the silver pure. This was commonly done by fire; and the idea is that He would make His own people pure by those judgments that would destroy His enemies who were intermingled with them.

Purely - The original word here - כבר kabor - has been commonly understood to mean, according to purity; that is, effectively or entirely pure. It is translated this way by the Septuagint and by the Latin Vulgate. But by the Chaldee it is translated, ‘I will purify you as with the herb borith.’ The word may mean lye, alkali, or potash (Job 9:30); and it may also mean borax—a substance formed of alkali and boracic acid, much used in purifying metals. The essential idea is, I will make you effectively or entirely pure.

Thy tin - For us, tin is a well-known white metal. But the word used here does not mean tin. It denotes the stannum of the ancients, a metal formed of lead mixed with silver ore. Here it means, I will take away all the impure metal mixed with you, varying the idea only slightly from the former part of the verse.