1 Timothy 1:5

Nothing is so injurious to mankind as to undervalue friendship; and not to cultivate it with the greatest care; as nothing, on the other hand, is so beneficial, as to pursue it to the utmost of our power. This Christ has shown, where He says, "If two of you shall agree on earth, as touching anything that they shall ask, it shall be done for them of My Father" (Matt. xviii. 19); and again, "Because iniquity shall abound, love shall wax cold." (Matt. xxiv. 12.) It is this that has been the occasion of all heresies. For men, because they loved not their brethren, have envied those who were in high repute, and from envying, they have become eager for power, and from a love of power have introduced heresies. On this account Paul having said, "that thou mightest charge some that they teach no other doctrine," now shows that the manner in which this may be effected is by charity. As therefore when he says, "Christ is the end of the Law" (Rom. x. 4), that is, its fulfillment, and this is connected with the former, so this a commandment implied in love. The end of medicine is health, but where there is health, there is no need to make much ado; so where there is love, there is no need of much commanding. But what sort of love does he speak of? That which is sincere, which is not merely in words but which flows from the disposition, from sentiment, and sympathy. "From a pure heart," he says, either with respect to a right conversation, or sincere affection. For an impure life too produces divisions. "For every one that doeth evil, hateth the light." (John iii. 20.) There is indeed a friendship even among the wicked. Robbers and murderers may love one another, but this is not "from a good conscience," not "from a pure" but from an impure "heart," not from "faith unfeigned," but from that which is false and hypocritical. For faith points out the truth, and a sincere faith produces love, which he who truly believes in God cannot endure to lay aside.