What constitutes a forbidden (Haram) oath?

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The forbidden oath is the false oath (perjury), which God condemned: "And they swear to falsehood while they know it" (Quran 58:14). Since lying is forbidden, swearing falsely on it intensifies the prohibition. If a false oath is used to invalidate a right or seize the property of a protected Muslim, the prohibition is severe. The Prophet warned that whoever takes a false oath to seize a Muslim's property, God will meet him in anger. Furthermore, swearing to commit a sin or neglect an obligation is forbidden because the object of the oath is unlawful, and the means adopted inherits the ruling of the end sought.