Disinterestedness is an essential condition of genuine friendship. Every service we render to our friend must be prompted by the desire to be of use to him. and not to advance our own interest. If any other motive enters our mind, if we speculate on his gratitude, and think that our kindness must eventually be returned with interest, we have no knowledge or feeling of friendship. Thus our Sages declare, “Friendship dictated by a selfish motive comes to an end together with the speculation; but friendship which is not based on any selfish motive comes never to an end. An instance of the first kind is the friendship between Amnon and Tamar (2 Sam. xiii.); of the second kind, the friendship between David and Jonathan (1 Sam. xviii.)” (Aboth v. 16). Friends bound to each other by genuine and sincere love find great pleasure in the fulfilment of the duties involved in friendship. They do not hesitate to bring sacrifices for each other’s well-being; they evince heartfelt sympathy for each other in good and evil fortune. All the duties of charity—gemilluth chesed—which we owe to our fellow-men in general, apply with increased force when our fellow-man is also our friend. One of these duties demands our special attention, because it is frequently neglected through human weakness: truthfulness and openness. Flattery, objectionable as it is in every case, is most detestable between friends. We must encourage our friends by kind words, and acknowledge their merits, but we must not spoil them by undue flattery. If, on the other hand, we discover errors or vices in our friend, it is our duty to communicate to him openly our opinion, and to do all that is in our power to bring him back to the path of righteousness and truth. “Thou shalt surely rebuke thy friend, and not suffer sin upon him” (Lev. xix. 17). Friendship is mostly formed without premeditation, and without any aim; we are friends, we do not know how and why; some similarity in our character, in our talents, in our views, in our successes and failures, or in our fortunes and misfortunes, draws us together, and we become friends before we are aware of the fact. But as far as we have control over our feelings we ought to be careful not to plunge into friendship without knowing something of the character and the tendencies of those with whom we are to associate ourselves in such close relationship. In Proverbs we are told, “Make no friendships with an angry man, and with a furious man thou shalt not go” (xxii. 24). Ben-sira (vi. 6) exhorts us, “If thou wouldst get a friend, prove him first, and be not hasty to credit him.” Our Sages say, “It is easy to make an enemy; it is difficult to make a friend” (Yalkut on Deut. vi. 16).