The word(s) "couldst" appears 13 time(s) in 13 verse(s) in Quran in Abdullah Yusuf Ali translation.

(1) If thou couldst but see when they are confronted with the Fire! They will say: "Would that we were but sent back! Then would we not reject the signs of our Lord, but would be amongst those who believe!"

(2) If thou couldst but see when they are confronted with their Lord! He will say: "Is not this the truth?" They will say: "Yea, by our Lord!" He will say: "Taste ye then the penalty, because ye rejected Faith."

(3) Who can be more wicked than one who inventeth a lie against Allah, or saith, "I have received inspiration," when he hath received none, or (again) who saith, "I can reveal the like of what Allah hath revealed"? If thou couldst but see how the wicked (do fare) in the flood of confusion at death! - the angels stretch forth their hands, (saying),"Yield up your souls: this day shall ye receive your reward,- a penalty of shame, for that ye used to tell lies against Allah, and scornfully to reject of His signs!"

(4) And Moses chose seventy of his people for Our place of meeting: when they were seized with violent quaking, he prayed: "O my Lord! if it had been Thy will Thou couldst have destroyed, long before, both them and me: wouldst Thou destroy us for the deeds of the foolish ones among us? this is no more than Thy trial: by it Thou causest whom Thou wilt to stray, and Thou leadest whom Thou wilt into the right path. Thou art our Protector: so forgive us and give us Thy mercy; for Thou art the best of those who forgive.

(5) If thou couldst see, when the angels take the souls of the Unbelievers (at death), (How) they smite their faces and their backs, (saying): "Taste the penalty of the blazing Fire-

(6) And (moreover) He hath put affection between their hearts: not if thou hadst spent all that is in the earth, couldst thou have produced that affection, but Allah hath done it: for He is Exalted in might, Wise.

(7) Then they proceeded: until, when they came to the inhabitants of a town, they asked them for food, but they refused them hospitality. They found there a wall on the point of falling down, but he set it up straight. (Moses) said: "If thou hadst wished, surely thou couldst have exacted some recompense for it!"

(8) Seest thou such a one as taketh for his god his own passion (or impulse)? couldst thou be a disposer of affairs for him?

(9) If only thou couldst see when the guilty ones will bend low their heads before their Lord, (saying:) "Our Lord! We have seen and we have heard: Now then send us back (to the world): we will work righteousness: for we do indeed (now) believe."

(10) The Unbelievers say: "We shall neither believe in this scripture nor in (any) that (came) before it." couldst thou but see when the wrong-doers will be made to stand before their Lord, throwing back the word (of blame) on one another! Those who had been despised will say to the arrogant ones: "Had it not been for you, we should certainly have been believers!"