Faith
When Paul here reckons faith among the fruits of the Spirit, it is manifest that he speaks not of faith which is in Christ, but of the fidelity and humanity of one man towards another. Hereupon he says in chapter 13 of the first to the Corinthians that charity believes all things. Therefore he that has this faith is not suspicious but mild, and takes all things to the best. And although he be deceived and finds himself to be mocked, yet such is his patience and softness, that he lets it pass. Briefly he is ready to believe all men, but he trusts not all. On the contrary, where this virtue is lacking, there men are suspicious, froward, wayward, dogged, and so neither will believe any thing, nor give place to any body. They can suffer nothing. Whatever a man says or does never so well, they cavil and slander it, so that whoever serves not their humor, can never please them. Therefore it is impossible for them to keep charity, friendship, concord, and peace with men. But if these virtues be taken away, what is this life else, but biting and devouring one of another? Faith therefore in this place is, when one man gives credit to another in things pertaining to this present life. For what manner of life should we lead in this world, if one man should not credit another?
When Paul lists faithfulness here among the fruits of the Spirit, it is plain that he is not speaking of faith in Christ but of the faithfulness and reliability that one person shows toward another. As he says in 1 Corinthians 13, love believes all things. The person who has this faithfulness is therefore not suspicious — he is gentle, and he interprets everything in the best possible light. Even when he is deceived and finds himself taken advantage of, his patience and goodwill are such that he lets it go. In short, he is ready to trust everyone — though he does not put blind confidence in everyone. Where this virtue is missing, people are suspicious, contrary, stubborn, and harsh — they will neither believe anyone nor give way to anyone. They can tolerate nothing. Whatever a person says or does, however well-intentioned, they find fault with it and slander it — so that no one who fails to serve their mood can ever please them. It becomes impossible for them to maintain love, friendship, harmony, or peace with others. And if these virtues are removed, what is life but biting and devouring one another? Faithfulness in this passage, then, is the willingness to take others at their word in the ordinary matters of daily life. For what kind of life would we have in this world if no one trusted anyone else?