Ibn 'Umar (May Allah be pleased with them) said:
A man mentioned to the Messenger of Allah (ﷺ) that he was often deceived in dealings. The Messenger of Allah (ﷺ) said to him, "When you enter into a transaction you should say: "There should be no deception."'[Al-Bukhari and Muslim].
App reference: Book 18, Hadith 72
Arabic/English book reference: Book 18, Hadith 1582