The word(s) "doubter" appears 3 time(s) in 3 verse(s) in Quran in Muhammad Habib Shakir translation.

(1) The truth is from your Lord, therefore you should not be of the doubters.

(2) And certainly Yusuf came to you before with clear arguments, but you ever remained in doubt as to what he brought; until when he died, you said: Allah will never raise an apostle after him. Thus does Allah cause him to err who is extravagant, a doubter

(3) Forbidder of good, exceeder of limits, doubter,