关于朋友的英语谚语，综合多个权威来源整理如下：

一、友谊的珍贵与难得

1. A friend is easier lost than found. 得朋友难，失朋友易

2. A friend in need is a friend indeed. 患难见真情

3. The more we love our friends, the less we flatter them. 真正的爱是少夸赞

4. Friendship is like a plant of slow growth. 友谊如细水长流

二、友谊的本质与表现

1. A friend is never known till a man has need. 需要时方显友情

2. Friends must part. 天下无不散之筵席

3. The friendship of a gentleman is insipid as water. 君子之交淡如水

4. A good friend is one who speaks well of us behind our backs. 背后说好话才是真朋友

三、友谊的维护与考验

1. To prepare a friend, honor him present, praise him absent, and assist him in his necessities. 维护朋友需尊重、表扬与帮助

2. Hypocritical friendship is like your shadow. 虚伪的友谊如影子般易逝

3. The smell of coin is often the knell of friendship. 铜臭味浓预示友谊危机

4. A faithful friend is hard to find. 益友难得

四、其他经典表述

1. Between friends all is common. 朋友之间无分彼此

2. Life without a friend is death. 没有朋友如死一般

3. The world is a wilderness without a friend. 没有朋友的世界如荒野

4. A friend is a single soul dwelling in two bodies. 朋友是两具躯壳共享同一灵魂

这些谚语从不同角度诠释了友谊的珍贵、本质、维护方式及考验标准，可作为理解西方文化中友情价值观的参考。