Jamieson, Fausset and Brown on Matthew 6:19

Mt 6:19-34. Concluding Illustrations of the Righteousness of the Kingdom--Heavenly-Mindedness and Filial Confidence.

19. Lay not up for ourselves treasures upon earth--hoard not.

where moth--a "clothes-moth." Eastern treasures, consisting partly in costly dresses stored up (Job 27:16), were liable to be consumed by moths (Job 13:28; Is 50:9; 51:8). In Jas 5:2 there is an evident reference to our Lord's words here.

and rust--any "eating into" or "consuming"; here, probably, "wear and tear."

doth corrupt--cause to disappear. By this reference to moth and rust our Lord would teach how perishable are such earthly treasures.

and where thieves break through and steal--Treasures these, how precarious!