The word(s) "doubt" appears 83 time(s) in 78 verse(s) in Quran in Abdullah Yusuf Ali translation.

(51) And thou wast not (able) to recite a Book before this (Book came), nor art thou (able) to transcribe it with thy right hand: In that case, indeed, would the talkers of vanities have doubted.

(52) "And be moderate in thy pace, and lower thy voice; for the harshest of sounds without doubt is the braying of the ass."

(53) (This is) the Revelation of the Book in which there is no doubt,- from the Lord of the Worlds.

(54) We did indeed aforetime give the Book to Moses: be not then in doubt of its reaching (thee): and We made it a guide to the Children of Israel.

(55) But he had no authority over them,- except that We might test the man who believes in the Hereafter from him who is in doubt concerning it: and thy Lord doth watch over all things.

(56) And between them and their desires, is placed a barrier, as was done in the past with their partisans: for they were indeed in suspicious (disquieting) doubt.

(57) "What! has the Message been sent to him - (Of all persons) among us?"... but they are in doubt concerning My (Own) Message! Nay, they have not yet tasted My Punishment!

(58) (David) said: "He has undoubtedly wronged thee in demanding thy (single) ewe to be added to his (flock of) ewes: truly many are the partners (in business) who wrong each other: Not so do those who believe and work deeds of righteousness, and how few are they?"... and David gathered that We had tried him: he asked forgiveness of his Lord, fell down, bowing (in prostration), and turned (to Allah in repentance).

(59) "And to you there came Joseph in times gone by, with Clear Signs, but ye ceased not to doubt of the (Mission) for which he had come: At length, when he died, ye said: 'No messenger will Allah send after him.' thus doth Allah leave to stray such as transgress and live in doubt,-

(60) "Without doubt ye do call me to one who is not fit to be called to, whether in this world, or in the Hereafter; our return will be to Allah; and the Transgressors will be Companions of the Fire!