The word(s) "truthful" appears 64 time(s) in 62 verse(s) in Quran in Saheeh International translation.

(1) And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful.

(2) And He taught Adam the names - all of them. Then He showed them to the angels and said, "Inform Me of the names of these, if you are truthful."

(3) Say, [O Muhammad], "If the home of the Hereafter with Allah is for you alone and not the [other] people, then wish for death, if you should be truthful.

(4) And they say, "None will enter Paradise except one who is a Jew or a Christian." That is [merely] their wishful thinking, Say, "Produce your proof, if you should be truthful."

(5) All food was lawful to the Children of Israel except what Israel had made unlawful to himself before the Torah was revealed. Say, [O Muhammad], "So bring the Torah and recite it, if you should be truthful."

(6) Those who said about their brothers while sitting [at home], "If they had obeyed us, they would not have been killed." Say, "Then prevent death from yourselves, if you should be truthful."

(7) [They are] those who said, "Indeed, Allah has taken our promise not to believe any messenger until he brings us an offering which fire [from heaven] will consume." Say, "There have already come to you messengers before me with clear proofs and [even] that of which you speak. So why did you kill them, if you should be truthful?"

(8) Allah - there is no deity except Him. He will surely assemble you for [account on] the Day of Resurrection, about which there is no doubt. And who is more truthful than Allah in statement.

(9) But the ones who believe and do righteous deeds - We will admit them to gardens beneath which rivers flow, wherein they will abide forever. [It is] the promise of Allah, [which is] truth, and who is more truthful than Allah in statement.

(10) They said, "We wish to eat from it and let our hearts be reassured and know that you have been truthful to us and be among its witnesses."