The word(s) "doubt" appears 60 time(s) in 58 verse(s) in Quran in Muhammad Pickthal translation.

(51) The (true) believers are those only who believe in Allah and His messenger and afterward doubt not, but strive with their wealth and their lives for the cause of Allah. Such are the sincere.

(52) Were We then worn out by the first creation? Yet they are in doubt about a new creation.

(53) Hinderer of good, transgressor, doubter,

(54) And he indeed had warned them of Our blow, but they did doubt the warnings.

(55) They will cry unto them (saying): Were we not with you? They will say: Yea, verily; but ye tempted one another, and hesitated, and doubted, and vain desires beguiled you till the ordinance of Allah came to pass; and the deceiver deceived you concerning Allah;

(56) And for such of your women as despair of menstruation, if ye doubt, their period (of waiting) shall be three months, along with those who have it not. And for those with child, their period shall be till they bring forth their burden. And whosoever keepeth his duty to Allah, He maketh his course easy for him.

(57) Till (the day) when they shall behold that which they are promised (they may doubt); but then they will know (for certain) who is weaker in allies and less in multitude.

(58) We have appointed only angels to be wardens of the Fire, and their number have We made to be a stumbling-block for those who disbelieve; that those to whom the Scripture hath been given may have certainty, and that believers may increase in faith; and that those to whom the Scripture hath been given and believers may not doubt; and that those in whose hearts there is disease, and disbelievers, may say: What meaneth Allah by this similitude? Thus Allah sendeth astray whom He will, and whom He will He guideth. None knoweth the hosts of thy Lord save Him. This is naught else than a Reminder unto mortals.