How we cite our quotes: (Book.Chapter.Bekker #s); all Bekker line numbers are approximate, since they are keyed to the original Greek.
Quote #1
For someone who accords with the middle characteristic here is the sort of person we mean by an equitable friend, if his disposition also goes together with feeling affection for the other. This characteristic differs from friendship, however, because it is without the relevant passion, that is, the feeling of affection for those with whom one associates...(4.6.1126b21-23)
Aristotle isn't really defining friendship here. Instead, he's talking about the virtue a person might have in relation to the people around him. If this were a Jane Austen novel, we might say that this person is "amiable"—someone who knows how to be friendly in a pleasing way. This virtue is the starting point for friendship, because without it, a person would not be properly sociable.
Quote #2
In poverty as well as in other misfortunes, people suppose that friends are their only refuge. And friendship is a help to the young, in saving them from error, just as it is also to the old, with a view to the care they require and their diminished capacity for action stemming from their weakness; it is a help also to those in their prime in performing noble actions, for 'two going together' are better able to think and to act. (8.1.1155a11-16)
We can't emphasize enough how much we agree with Aristotle here: you always need your buds. There's no time of life when we can make it on our own—or if we can, it is always much more pleasant to have a companion to share in our lives. Again, Aristotle's not getting all Hallmark Channel on us here: he's totally practical. As humans, we need another set of hands, brains, and a shoulder to cry on in order to lead stable and productive lives.
Quote #3
When people are friends, they have no need of justice, but when they are just, they do need friendship in addition; and in the realm of the just things, the most just seems to be what involves friendship. Yet friendship is not only necessary but also noble, for we praise those who love their friends, and an abundance of friends is held to be a noble thing. Further, people suppose good men and their friends to be one and the same. (8.1.1155a26-31)
What exactly is it about friendship that makes justice a secondary concern? Aristotle will later posit that it's because we see our friend as a second self, and it is very nearly impossible to do an injustice to ourselves. This automatic sense of justice between friends also allows other virtues to surface, or at least makes it easier for the good side to come out.
Because of this, we always think of our friends as the "best"—kind, worthy, good people. Which is why we always ask a friend for a job recommendation, and not just anyone. And although Aristotle later tells us that we really shouldn't have many great friends, we do feel that he or she who winds up with the most friends wins.