But let every man prove his own work, and then shall he have rejoicing in himself alone, and not in another.
Ver. 4. But let every man prove] This is an excellent remedy against self-deceit, and a means to make one fit to reprove others with mercy and meekness.
And then shall he have rejoicing] Ut testimonium perhibeat conscientia propria, non lingua aliena, saith Augustine, that thine own conscience and not another man's tongue may testify for thee. Omnis Sarmatarum virtus extra ipsos, saith Tacitus. All the self-deceiver's goodness is shored up by popularity or other base respects.