John Calvin Commentary 1 John 3:18

"[My] Little children, let us not love in word, neither with the tongue; but in deed and truth." — 1 John 3:18 (ASV)

Let us not love in word. There is a concession in this first clause. For while we cannot truly love in tongue only, many falsely pretend to do so. Therefore, the Apostle, as is often done, concedes the term itself to their pretense. However, in the second clause, he rebukes their emptiness by denying that there is any reality to such love except in action.

The words should be explained in this way: let us not profess by the tongue that we love, but prove it by the deed, for this is the only true way of showing love.