What is the obligation for one who can visually perceive the Ka'bah during prayer?

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If one can visually perceive the Ka'bah, the obligation is to pray directly towards its exact self (Ain). There is no known disagreement on this matter. If any part of the worshipper falls outside the perpendicular line (musāmat) of the Ka'bah, the prayer is invalid, according to Ibn Aqil.