1To do, carry out, or bring about (a result); a somewhat literary, formal transitive verb. Seen in set phrases such as 為す術がない (be at a loss for what to do), 為せば成る (where there's a will there's a way), and 為すべきこと (what ought to be done). Usually written in kana. (Essentially the same as the 'to do' sense of 成す.)
為せば成る、為さねば成らぬ何事も。
Where there's a will there's a way; nothing gets done if you don't try.
彼は生涯をかけて大事を為した。
He accomplished a great undertaking over the course of his life.
悪事を為した者は、いつか裁かれる。
Those who commit evil deeds will be judged someday.