The word(s) "truthful" appears 63 time(s) in 62 verse(s) in Quran in Muhammad Habib Shakir translation.

(11) Eight in pairs-- two of sheep and two of goats. Say: Has He forbidden the two males or the two females or that which the wombs of the two females contain? Inform me with knowledge if you are truthful.

(12) And to those who were Jews We made unlawful every animal having claws, and of oxen and sheep We made unlawful to them the fat of both, except such as was on their backs or the entrails or what was mixed with bones: this was a punishment We gave them on account of their rebellion, and We are surely truthful.

(13) They said: Have you come to us that we may serve Allah alone and give up what our fathers used to serve? Then bring to us what you threaten us with, if you are of the truthful ones.

(14) He said: If you have come with a sign, then bring it, if you are of the truthful ones.

(15) Surely those whom you call on besides Allah are in a state of subjugation like yourselves; therefore call on them, then let them answer you if you are truthful.

(16) Or do they say: He has forged it? Say: Then bring a chapter like this and invite whom you can besides Allah, if you are truthful.

(17) And they say: When will this threat come about, if you are truthful?

(18) Or, do they say: He has forged it. Say: Then bring ten forged chapters like it and call upon whom you can besides Allah, if you are truthful.

(19) They said: O Nuh! indeed you have disputed with us and lengthened dispute with us, therefore bring to us what you threaten us with, if you are of the truthful ones.

(20) They said: O our father! surely we went off racing and left Yusuf by our goods, so the wolf devoured him, and you will not believe us though we are truthful.