2 verses have
truthful
in Edition Clear Qur'an by Talal Itani / Hud (Hud)

11:13Or do they say, “He invented it?” Say, “Then produce ten chapters like it, invented, and call upon whomever you can, besides God, if you are truthful.”

11:32They said, “O Noah, you have argued with us, and argued a great deal. Now bring upon us what you threaten us with, if you are truthful.”