关于朋友的英语谚语，综合多个权威来源整理如下：

一、友谊的珍贵性

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

2. The best of friends must part. 天下没有不散的宴席。

3. Friendship is like a plant of slow growth. 友谊像生长着的植物，是慢慢地建立起来的。

4. A good book is the best of friends, the same today and forever. 好书如挚友，情谊永不渝。

二、友谊的本质

5. Friendship is almost always the union of a part of one mind with a part of another. 朋友是两者思想的结合，志趣相投。

6. A friend is never known till a man has need. 需要之时方知友。

7. The true friendship seeks to give, not take； to help, not to be helped. 真正的友谊是付出而非索取。

8. What is a friend？ A single soul dwelling in two bodies. 朋友是什么？两副躯壳拥有同一灵魂。

三、友谊的维护

9. Be true to your word, your work, and your friend. 人应遵守诺言，忠实于工作和友人。

10. A faithful friend is hard to find. 真挚的朋友难觅。

11. The heart is seen in wine. 酒后吐真言（隐喻真诚在困境中显现）。

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

四、友谊的持久性

13. Time is money, but time is money with a friend. 金钱易得，友情难寻。

14. The roots of friendship run deep. 友谊的根基深厚。

15. I know not whether our names will be immortal； I am sure our friendship will. 名字难留，友情长存。

五、其他经典表述

16. A friend is like a good movie: you never know what you're going to get. 朋友如电影，充满惊喜。

17. The best revenge is massive success. 最好的报复是成功。

18. A friend is one who walks in when the rest of the world walks out. 朋友是在众人离场时仍能相伴的人。

19. The true test of friendship is not how often you see each other, but how you remember the last time you did. 友谊的真正考验不在于见面频率，而在于是否铭记过往。

20. A friend is someone who sees the good in you and helps you see the good in yourself. 朋友是能让你看到自身美好并鼓励你的人。

注：部分谚语存在中英文表述差异（如"set great store by friendship"与"友情重千斤"），但核心含义一致。建议根据具体语境选择使用。