27 I have made you a tester of metals and a fortress among my people; that you may know and try their way. 28 They are all grievous rebels, going about with slanders; they are brass and iron: they all of them deal corruptly. 29 The bellows blow fiercely; the lead is consumed of the fire: in vain do they go on refining; for the wicked are not plucked away. 30 Men will call them rejected silver, because Yahweh has rejected them.
Matthew Henry's Commentary on Jeremiah 6:27-30
Commentary on Jeremiah 6:18-30
(Read Jeremiah 6:18-30)
God rejects their outward services, as worthless to atone for their sins. Sacrifice and incense were to direct them to a Mediator; but when offered to purchase a license to go on in sin, they provoke God. The sins of God's professing people make them an easy prey to their enemies. They dare not show themselves. Saints may rejoice in hope of God's mercies, though they see them only in the promise: sinners must mourn for fear of God's judgments, though they see them only in the threatenings. They are the worst of revolters, and are all corrupters. Sinners soon become tempters. They are compared to ore supposed to have good metal in it, but which proves all dross. Nothing will prevail to part between them and their sins. Reprobate silver shall they be called, useless and worthless. When warnings, corrections, rebukes, and all means of grace, leave men unrenewed, they will be left, as rejected of God, to everlasting misery. Let us pray, then, that we may be refined by the Lord, as silver is refined.