You might be referring to 위해 and 위해서. 위해(서) is the closes word for "for" or "for the sake/purpose of". - 이 박사는 질병 퇴치를 위해 평생을 바쳤다 - Doctor Lee dedicated his whole life to fighting diseases. - 아들의 성공을 위해서 못할 일이 없다 - There's nothing I wouldn't do to help my son to succeed. - 모든 인류를 위해서 - For the sake of all mankind.

Hi, Putri! Did you mean 왜 해 and 왜 해서 which mean "Why you did~" or Did you mean 의해~and 의해서 meaning "by~, because of ~, according to~"??? If latter (I am guessing so..) here are some examples .. 1, 결과에 의해서 결정하겠다. I will make a decision according to/depending on the result. 2, 나는 연구 결과에 의해 글을 쓰겠다. I will write a report according to the result of studies. Both of them are used pretty in the same situation.. especially when something is settled with final comeouts. So basically means depending on/according to/being based on...etc Please Google or Naver them for more examples in other sentences! :D