EXOD377 The virtues of solitude and the ill effects of association with fools. When a person's soul longs for the company and comraderie of other people, he should reflect on the virtues of solitude and separation from others, and on the ill effects of associating with fools when this is not absolutely necessary. Among the ill effects of companionship with them is ... false and trivial oaths, of which the Creator has said: “God will not allow it to go unpunished” (Shemos 20:7). A pious man once said to his disciples, “The Torah has permitted us to swear truthfully in God's Name; but I advise you not to swear by His Name [at all], either truthfully or falsely. Just say, ‘It is so,’ or ‘It is not so.’” … Another “[consequence of their company] is the obligation to enjoin right conduct and warn against evil, as we were commanded by the Creator when He said: “You must reprove your fellow” (Vayikra 19:17). We are obligated to object to evil in three ways: (1) by striking it with the hand, as manifested in the incident of Zimri and Kazbi; (2) by objecting in words, as Moshe [our Master] did when he said to the wrongdoer, “Why are you striking your fellow?” (Shemos 2:13); and (3) by [objecting] in one's heart, as David, peace be upon him, said: “I hate a crowd of evildoers and will not sit with the wicked” (Tehillim 26:5). If one can intercede with force and does not do so, he is delinquent. If he cannot intercede with force, he should object verbally. And if he cannot object verbally, he should object in his heart. Thus we are bound to object to evildoers under all circumstances, as the uneducated inevitably fall short of filling their duty. When you are alone, however, you are undoubtedly excused from the duty to enjoin good and warn against evil, which is a duty difficult duty to fulfill and discharge, as our Sages, of beloved memory, said: “I doubt if there is anyone in this generation who can accept reproof ... I doubt if there is anyone in this generation who knows how to reprove.” (Arachin 16b).