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].

وعنه قال: ذكر رجل لرسول الله ﷺ أنه يُخدع في البيوع فقال رسول الله ﷺ: "من بايعت؟ فقل : لا خلابة" ((متفق عليه)). "الخِلابة" بخاء معجمة مكسورة، وباء موحدة: وهي الخديعة.