Lay not up for yourselves treasures upon earth, where moth and rust doth corrupt, and where thieves break through and steal: Lay not up for yourselves treasures upon earth - What blindness is it for a man to lay up that as a treasure which must necessarily perish! A heart designed for God and eternity is terribly degraded by being fixed on those things which are subject to corruption. "But may we not lay up treasure innocently?" Yes.
1st. If you can do it without setting your heart on it, which is almost impossible: and
2dly. If there be neither widows nor orphans, destitute nor distressed persons in the place where you live.
"But there is a portion which belongs to my children; shall I distribute that among the poor?" If it belongs to your children, it is not yours, and therefore you have no right to dispose of it. "But I have a certain sum in stock, etc.; shall I take that and divide it among the poor?" By no means; for, by doing so, you would put it out of your power to do good after the present division: keep your principal, and devote, if you possibly can spare it, the product to the poor; and thus you shall have the continual ability to do good. In the mean time take care not to shut up your bowels of compassion against a brother in distress; if you do, the love of God cannot dwell in you.
Rust - Or canker, βρωσις, from βρωσκω, I eat, consume. This word cannot be properly applied to rust, but to any thing that consumes or cankers clothes or metals. There is a saying exactly similar to this in the Institutes of Menu: speaking of the presents made to Brahmins, he says, "It is a gem which neither thieves nor foes take away, and which never perishes." Chapter of Government, Institute 83.
Where thieves do not break through - Διορυσσουσι, literally dig through, i.e. the wall, in order to get into the house. This was not a difficult matter, as the house was generally made of mud and straw, kneaded together like the cobb houses in Cornwall, and other places. See Clarke on Matthew 7:27 (note).