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

(41) So, by thy Lord, without doubt, We shall gather them together, and (also) the Evil Ones (with them); then shall We bring them forth on their knees round about Hell;

(42) "But, without doubt, I am (also) He that forgives again and again, to those who repent, believe, and do right, who,- in fine, are ready to receive true guidance."

(43) O mankind! if ye have a doubt about the Resurrection, (consider) that We created you out of dust, then out of sperm, then out of a leech-like clot, then out of a morsel of flesh, partly formed and partly unformed, in order that We may manifest (our power) to you; and We cause whom We will to rest in the wombs for an appointed term, then do We bring you out as babes, then (foster you) that ye may reach your age of full strength; and some of you are called to die, and some are sent back to the feeblest old age, so that they know nothing after having known (much), and (further), thou seest the earth barren and lifeless, but when We pour down rain on it, it is stirred (to life), it swells, and it puts forth every kind of beautiful growth (in pairs).

(44) And verily the Hour will come: there can be no doubt about it, or about (the fact) that Allah will raise up all who are in the graves.

(45) Those who reject Faith will not cease to be in doubt concerning (Revelation) until the Hour (of Judgment) comes suddenly upon them, or there comes to them the Penalty of a Day of Disaster.

(46) Is it that there is a disease in their hearts? or do they doubt, or are they in fear, that Allah and His Messenger will deal unjustly with them? Nay, it is they themselves who do wrong.

(47) Without doubt it is (announced) in the mystic Books of former peoples.

(48) Still less can their knowledge comprehend the Hereafter: Nay, they are in doubt and uncertainty thereanent; nay, they are blind thereunto!

(49) Qarun was doubtless, of the people of Moses; but he acted insolently towards them: such were the treasures We had bestowed on him that their very keys would have been a burden to a body of strong men, behold, his people said to him: "Exult not, for Allah loveth not those who exult (in riches).

(50) Recite what is sent of the Book by inspiration to thee, and establish regular Prayer: for Prayer restrains from shameful and unjust deeds; and remembrance of Allah is the greatest (thing in life) without doubt. And Allah knows the (deeds) that ye do.