James 5:3

Your gold and your silver are rusted; and their rust shall be for a testimony against you, and shall eat your flesh as fire. Ye have laid up your treasures in the last days.

Gold ... silver ... rusted ... The precious metals themselves did not rust, of course, and James certainly knew that; but the base alloys evil men had mixed with them did rust. The gold and silver of the Sadducean enemies were in no sense "pure," but they had been mixed with fraud, deceit, oppression, falsehood and murder; and the metaphor of rusted gold and silver is eloquent. Even the most precious assets would be of no avail when the judgment fell.

A testimony against you ... As the blood of righteous Abel cried unto God, just so the Sadducean wealth of Jerusalem would cry to heaven for vengeance. Long centuries of God's forbearance and patient love, still spurned, still contemptuously rejected, would at last reap their inevitable harvest.

And shall eat your flesh as fire ... This is a metaphor. The woes coming upon them were, in fact, caused by their inordinate love of that very wealth so avidly and fraudulently acquired; thus it was appropriate to say that the wicked riches unjustly extorted and wickedly abused would indeed eat their flesh as fire. Punchard declared that "The wages of the traitor, the spoil of the thief, and the wealth of the oppressor burn the hands that clasp them. Memories of the wrongs shiver through each guilty soul like fire."[8]

Dummelow referred this to "the siege of Jerusalem."[9] Likewise, Carson:

The last days were already upon them. The Christian is always in the last days (Acts 2:17; 1 John 2:18). The reference is to the last days before the Second Advent, of which the destruction of Jerusalem was a type.[10]

In the destruction of Jerusalem, the wealthy Sadduceans lost all of their wealth, and more than a million were ruthlessly murdered, fulfilling perfectly the promise of Jesus that "The king was wroth; and he sent his armies, and destroyed those murderers, and burned their city" (Matthew 22:7). This was "the last days" of the Jewish commonwealth.

Despite the Old Testament overtones of this passage, the spirit and teaching of the New Testament also permeate it, as indicated by this reference to "the last days," and the laying up of treasures where moth and rust doth consume (James 5:2), a plain reference to Jesus' teaching in Matthew 6:20f.

[8] E. G. Punchard, op. cit., p. 375.

[9] J. R. Dummelow, Commentary on the Holy Bible (New York: The Macmillan Company, 1937), p. 1037.

[10] T. Carson, A New Testament Commentary (Grand Rapids, Michigan: Zondervan Publishing House, 1969), p. 580.