John Gill Bible Commentary

Again they are minished,.... Or "lessened", in their families, cattle, and substance; either the same persons as before, or others. The Targum paraphrases it, "but when they sin, they are lessened:'' for sin is the cause of it, as follows: and brought low through oppression, affliction and sorrow; either because of their oppression of the poor, the evil they do to them, and the sorrow they bring upon them; or they are brought into a low estate through the tyranny and oppression of others, and by the afflictions and sorrows they are brought into by them. This may be applied to the Jews, at their destruction by the Romans, when they were greatly lessened and brought low by their oppression of them: or rather to the Christians; not under the Heathen persecutions, for then they increased more and more; but under antichristian tyranny, when the beast had power over them, and overcame and slew them; and their numbers were so reduced, that the whole world is said to wonder after the beast, Rev 13:3, and which will be the case again, when the witnesses will be slain: the number of Christians is greatly lessening now; there are but a few names in Sardis; Jacob is small, but will be smaller and fewer still.