A man in need is a man in need ,请问这句要怎么翻译才信达雅,还有这句话是出自哪里,谢谢!

患难之交见真情.
原文：Two friends are waiking in the is thin and tall,and very bad other is fat and short,and very tall man says to the short man ,"we are good friends,if any beast comes at all,I will help you ."The short man say :"of course,we are good friends we will help each other."
At that time,a bear comes to almost comes very tall man climbs up the tree the fat man can not climb the says:"Help me !Help me!I can not climb !The bear is coming!"The tall man says:"No!No!You can not stay with tree is not strong."The bear is short man lies down below the tree,posing as dead and holds his bear smells around his does not touch the death.
After the bear went away without harming the short man ,The tall man comes down and asks the fat man:"what did the bear whisper into your ears when it closed to you?"The short man answer:"The bear told me not to trust such selfish friend like you very also said a friend in need is really a friend indeed."