These are spots in your feasts of charity, when they feast with you, feeding themselves without fear: clouds they are without water, carried about of winds; trees whose fruit withers, without fruit, twice dead, plucked up by the roots;
Raging waves of the sea, foaming out their own shame; wandering stars, to whom is reserved the blackness of darkness for ever.
1. "These are spots in your feasts." False teachers are blemishes, partaking to themselves but contributing nothing.
2. They are "clouds without water, carried about of winds." False teachers drift like clouds above a semiarid land, holding out the promise of rain, but containing no water. They are blown about by capricious winds, providing nothing.
3. They are "trees whose fruit withers." A tree that bears no fruit is useless, dead; and these are twice-dead, for they have been uprooted from truth.
4. They are "raging waves of the sea, foaming out their own shame." Picture the wind-blown waves dashing against the walls of stone along the shore, the spray flying every which way, accomplishing only the erosion of the rocks. Such is the effect of false teachers on the body of believers.
5, False teachers are "wandering stars, to whom is reserved the blackness of darkness forever." Travelers in the desert or on the seas may use a fixed star, e.g., the Pole Star for guidance. But to rely on a heavenly body whose position varies with the motions of the celestial realm is to be misled, lost. To rely on such teachers is to be lost. Note, too, the fate of such "stars."
It is imperative that we check any teaching within the Church against the navigational chart given us by God, that is The Holy Bible. All teachings must be supported by scripture, else we will be led astray.