I say then: It is well known that friends are something that is necessary for man throughout his whole life. Aristotle has already set this forth in the ninth book of the “Ethics.” For in a state of health and happiness a man takes pleasure in their [i.e. friend’s] familiar relationship with him; in adversity he has recourse to them; and in his old age when his body is grown weak he seeks their help. The same things may be found to a much greater extent in the relationship with one’s children and also in the relationship with one’s relatives. For fraternal sentiments and mutual love and mutual help can be found in their perfect form only among those who are related by ancestry. Accordingly a single tribe that is united through a common ancestor—even if he is remote—because of this, love one another, help one another, and have pity on one another, and the attainment of these things is the greatest purpose of the Law.
Moreh Nevuchim 3-49