你应该尽快做必须做的事。

You should do what is needful as soon as possible.

youdao

答应做必须做的事。

I'll do what I must.

youdao

答应做必须做的事。

I must do this and I must do that.

youdao

We've extrapolated that people have property rights and so whether or not it would be a good thing or a nice thing or even a necessary thing for the survival of some people, we don't see that that justifies the violation of the right that we've logically extrapolated.

我们已经推出人们有财产权,所以，就算是为了做好事，做善事,甚至是为了让某些人活下去而必须做的事，那也是不能证明，侵犯这些推定的权利,就是正当的。

耶鲁公开课 - 公正课程节选

you can use the "you have to" pattern to express something that somebody else really must do.

你可以用“you have to”句型表明一些其他人必须做的事。

have to 课堂 - SpeakingMax英语口语达人

Non-Western peoples who wish to share in the things that characterize modernity will need to study the ideas and history of Western civilization to achieve what they want, and westerners, I would argue, who wish to preserve these things must do the same.

希望分享西方现代特点的,非西方人士需要学习,西方文明的思想和历史,以实现自己的理想,而对西方,而我要说,那些希望,保留自身文明的西方人,也必须做相同的事

耶鲁公开课 - 古希腊历史简介课程节选