Usage of the character 必

lit. when we get to the mountain, there'll be a way through (idiom)
fig. everything will turn out for the best; let's worry about it when it happens; it will be all right on the night

jìyǒujīnrìhébìdāngchū

既有今日何必当初

[既有今日何必當初]

see 早知今日何必當初／早知今日何必当初 (zǎozhījīnrìhébìdāngchū)

sānrénxíng,bìyǒuwǒshī

三人行，必有我师

[三人行，必有我師]

lit. if three walk together, one can be my teacher (idiom, from the Analects of Confucius)
you have sth to learn from everyone

yǒuqíshī,bìyǒuqítú

有其师，必有其徒

[有其師，必有其徒]

As the teacher, so the pupil. (idiom)

zǎozhījīnrìhébìdāngchū

早知今日何必当初

[早知今日何必當初]

if I (you, she, he...) had known it would come to this, I (you, she, he...) would not have acted thus (idiom)
to regret vainly one's past behavior

kòngxuéláifēngwèibìwúyīn

空穴来风未必无因

[空穴來風未必無因]

wind does not come from an empty cave without reason
there's no smoke without fire (idiom)

sānrénxíng,zébìyǒuwǒshī

三人行，则必有我师

[三人行，則必有我師]

If three walk together, one of them can teach me sth (Confucius)

liǎnghǔxiāngdòu,bìyǒuyīshāng

两虎相斗，必有一伤

[兩虎相鬥，必有一傷]

lit. when two tigers fight, one will get injured (idiom)
fig. if it comes to a fight, someone will get hurt

xiǎoshíliǎoliǎo,dàwèibìjiā

小时了了，大未必佳

[小時了了，大未必佳]

being bright at an early age does not necessarily bring success upon growing up (proverb)

èrhǔxiāngdòu,bìyǒuyīshāng

二虎相斗，必有一伤

[二虎相鬥，必有一傷]

lit. when two tigers fight, one is sure to be wounded (idiom)
fig. if it comes to a fight, someone will get hurt

dànànbùsǐ,bìyǒuhòufú

大难不死，必有后福

[大難不死，必有後福]

one is bound for good fortune after surviving a great disaster (proverb)

débùpèiwèi,bìyǒuzāiyāng

德不配位，必有灾殃

[德不配位，必有災殃]

calamity will befall those whose moral standards are not in keeping with their social status

zhìzhěqiānlü,bìyǒuyīshī

智者千虑，必有一失

[智者千慮，必有一失]

lit. a wise person reflecting a thousand times can still make a mistake (idiom); fig. nobody is infallible

fēnjiǔbìhé,héjiǔbìfēn

分久必合，合久必分

[分久必合，合久必分]

lit. that which is long divided must unify, and that which is long unified must divide (idiom, from 三國演義／三国演义 ( Sānguó Yǎnyì))
fig. things are constantly changing

liǎnghǔxiāngzhēng,bìyǒuyīshāng

两虎相争，必有一伤

[兩虎相爭，必有一傷]

lit. if two tigers fight, one will get injured (idiom)
fig. if you start a war, someone is bound to get hurt

rénwúyuǎnlü,bìyǒujìnyōu

人无远虑，必有近忧

[人無遠慮，必有近憂]

He who gives no thought to far-flung problems soon finds suffering nearby (idiom, from Analects).
Smug concentration on the here and now will lead to future sorrow.

yùshànqíshì,bìxiānlìqíqì

欲善其事，必先利其器

[欲善其事，必先利其器]

To do a good job, an artisan needs the best tools (idiom). Good tools are prerequisite to the successful execution of a job

gōngyùshànqíshì,bìxiānlìqíqì

工欲善其事，必先利其器

[工欲善其事，必先利其器]

To do a good job, an artisan needs the best tools (idiom). Good tools are prerequisite to the successful execution of a job

chēdàoshānqiánbìyǒulù,chuándàoqiáotóuzìránzhí

车到山前必有路，船到桥头自然直

[車到山前必有路，船到橋頭自然直]

(idiom) everything will turn out all right; let's worry about it when it happens; it will be all right on the night