مَنْ غَشَّنَا، فَلَيْسَ مِنَّا
Whoever deceives us is not following our way.
Source: مسلم
غَشَّ means “deceived” or concealed a material truth. In غَشَّنَا, the pronoun نَا is the object, “us.” The response فَلَيْسَ مِنَّا is a forceful warning against deception, not a mechanical ruling about an individual person's faith.
Concealing a product defect, misrepresenting facts in a transaction, cheating on an examination, or exploiting another person's trust are examples of dishonesty. Fair dealings allow the other party to make an informed decision. Trust grows when people disclose relevant facts and fulfill what they promise.