7 For every kind of beasts. This is a confirmation of the last clause; for that Satan by the tongue rules most effectively he proves by this — that it can by no means be brought to due order; and he amplifies this by comparisons. For he says that there is no animal so savage or fierce, which is not tamed by the skill of man, — that fishes, which in a manner inhabit another world, — that birds, which are so quick and roving — and that serpents, which are so inimical to mankind, are sometimes tamed. Since then the tongue cannot be restrained, there must be some secret fire of hell hidden in it.
What he says of wild beasts, of serpents, and of other animals, is not to be understood of them all; it is enough that the skill of man should subdue and tame some of the most ferocious of them, and also that serpents are sometimes tamed. He refers to present and to past time: the present regards power and capacity, and the past, usage or experience. He hence justly concludes that the tongue is full of deadly poison.
Though all these things most suitably refer in the first place to the subject of this passage — that they claim an unreasonable command over others, who labor under a worse vice; yet a universal doctrine may be understood as taught here, — that if we desire to form our life aright, we must especially strive to restrain the tongue, for no part of man does more harm.