Do not have evil-doers for friends, do not have low people for friends: have virtuous people for friends, have for friends the best of men. The Dhammapada
Yes, we must ever be friends; and of all who offer you friendship let me be ever the first, the truest, the nearest and dearest! Henry Wadsworth Longfellow
When a man laughs at his troubles he loses a great many friends. They never forgive the loss of their prerogative. H.L. Mencken
A doubtful friend is worse than a certain enemy. Let a man be one thing or the other, and we then know how to meet him. Aesop
Friendship is composed of a single soul inhabiting two bodies. Titus Maccius Plautus
Friendship is almost always the union of a part of one mind with the part of another; people are friends in spots. George Santayana
Greater love hath no man than this, that a man lay down his life for his friends. (John 15:13, KJV) Bible
A man cannot be said to succeed in this life who does not satisfy one friend. Henry David Thoreau
The holy passion of Friendship is of so sweet and steady and loyal and enduring a nature that it will last through a whole lifetime, if not asked to lend money. Mark Twain