A seller knows that an item has a significant defect but conceals it to secure payment. Withholding that information is a clear practical instance of غَشَّنَا. Likewise, presenting another student's work as one's own conceals the truth about one's abilities and effort.
Example 1: Disclose a known material defect before a sale and keep the terms of the transaction clear.
Example 2: Acknowledge what was done by others instead of claiming their work as one's own.
Deception can appear to produce a quick advantage, but it violates rights and undermines the trust on which fair learning and commerce depend.