What is the ruling if a man's semen comes into contact with impurity on his genitals before emission?

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If a man's semen comes into contact with impurity on his genitals, the semen itself becomes impure, and no pardon is granted for a minor amount of it due to that contact. Al-Qadi suggested that semen resulting from intercourse is impure because it cannot be free from penile discharge (madhy). This is refuted because the semen of the Prophet (peace be upon him) resulted from intercourse, and the rulings of purity derived for others are based on his semen.