Adam Clarke on 2 Timothy 2:17

Their word will eat as doth a canker - Ὡς γαγγραινα· As a gangrene; i.e. as a mortification in the flesh, where the circulation is entirely stopped, and putrefaction takes place, which continues to corrupt all the circumjacent flesh, spreading more and more till death takes place, unless stopped by a timely and judicious application of medicine. Such is the influence of false doctrine; it fixes its mortal seed in the soul, which continues to corrupt and assimilate every thing to itself, till, if not prevented by a timely application of the word of life, under the direction of the heavenly Physician, it terminates in the bitter pains of an eternal death. To such a gangrene the apostle compares the corrupt doctrines of Hymeneus and Philetus.