I was surprised to note that John ended his letter with this word of exhortation. I couldn’t find his use of the word “idol(s)” anywhere else. Others yes, but not John.
1 John 5:21
Little children, keep yourselves from idols, Amen. From Heathen idols and idolatry, into which the saints in those times might be liable to be drawn, by reason of their dwelling among Heathen idolaters, and being related to them, and by the too great freedom used in eating things sacrificed to idols in their temples; and from all other idols that might be introduced by some who went by the name of Christians, as the Gnostics, who worshipped the images of Simon and Helena; and the passage may be an antidote against the worshipping of images, afterwards introduced by the Papists. Moreover, errors and false doctrines, which are the figments of men’s minds, and what they are fond of, may be called idols, and should be guarded against, and abstained from; as also the lusts of men’s hearts, and all the evil things that are in the world, which are adored by the men of it; and even every creature that is loved too much is an idol; hence covetousness is called idolatry; nor should any creature or thing be loved more than God or Christ: the one only living and true God, Father, Son, and Spirit, he is only to be worshipped, feared, and loved.