Unto was used to indicate that something was done or given to someone.
例句
And he said unto him, 'Who is my neighbor?'...他于是對他說道：“誰是我鄰居？”I will do unto others what they did to me.我會以其人之道還治其人之身。
PREP
迄至；直至；直到
Unto was used to indicate that something continued until a particular time.
例句
Be ye faithful unto the end.汝等應至死不渝。
英漢詞典釋義
prep.
對,向
Do unto others as you would have them do unto you.己所不欲,勿施于人。No matter how high one’s position,he must never be a law unto himself.無論一個人的職位有多高,都絕對不能獨斷專行。