The word(s) "truthful" appears 11 time(s) in 11 verse(s) in Quran in Abdullah Yusuf Ali translation.

(1) And they say: "None shall enter Paradise unless he be a Jew or a Christian." Those are their (vain) desires. Say: "Produce your proof if ye are truthful."

(2) Allah will say: "This is a day on which the truthful will profit from their truth: theirs are gardens, with rivers flowing beneath,- their eternal Home: Allah well-pleased with them, and they with Allah: That is the great salvation, (the fulfilment of all desires).

(3) Say: "Think ye to yourselves, if there come upon you the wrath of Allah, or the Hour (that ye dread), would ye then call upon other than Allah?- (reply) if ye are truthful!

(4) (Take) eight (head of cattle) in (four) pairs: of sheep a pair, and of goats a pair; say, hath He forbidden the two males, or the two females, or (the young) which the wombs of the two females enclose? Tell me with knowledge if ye are truthful:

(5) Verily those whom ye call upon besides Allah are servants like unto you: Call upon them, and let them listen to your prayer, if ye are (indeed) truthful!

(6) "Now cause a piece of the sky to fall on us, if thou art truthful!"

(7) They also say: "When will this promise (come to pass)? (Say) if ye are truthful."

(8) Say: "Then bring ye a Book from Allah, which is a better guide than either of them, that I may follow it! (do), if ye are truthful!"

(9) Then bring ye your Book (of authority) if ye be truthful!

(10) Say: "O ye that stand on Judaism! If ye think that ye are friends to Allah, to the exclusion of (other) men, then express your desire for Death, if ye are truthful!"