How is the killing justified if no direct witnesses are present but the husband claims justification based on finding the man with his wife?

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If there is no direct evidence (bayanah) but the guardian confirms the husband's knowledge of the situation, the guardian's word, accompanied by an oath, is accepted. In the case of the man killed after writing a poem indicating his adultery with a warrior's wife, Umar excused the killer and did not demand retaliation because the justification was established through the guardian's admission.