John Calvin Commentary Galatians 5:15

"But if ye bite and devour one another, take heed that ye be not consumed one of another." — Galatians 5:15 (ASV)

But if you bite and devour one another. From the nature of the subject, as well as from the language used, we may conjecture that the Galatians had disputes among themselves, because they differed about doctrine. The apostle now demonstrates, from the result, how destructive such proceedings in the church must ultimately prove to be. False doctrine was probably a judgment from heaven on their ambition, pride, and other offenses. This may be concluded from what frequently happens in the divine dispensations, as well as from an express declaration by the hand of Moses.

You shall not listen to the words of that prophet, or that dreamer of dreams; for the Lord your God tests you, to know whether you love the Lord your God with all your heart, and with all your soul. (Deuteronomy 13:3).

By biting and devouring he means, I think, slanders, accusations, reproaches, and every other kind of offensive language, as well as acts of injustice arising either from fraud or violence. And what is the end of them? To be consumed, while the tendency of brotherly love is to produce mutual protection and kindness. I wish we could always remember, when the devil tempts us to disputes, that the disagreement of members within the church can lead to nothing else than the ruin and consumption of the whole body. How distressing, how mad is it, that we, who are members of the same body, should be leagued together, of our own accord, for mutual destruction!