The Shaykh (Al-Mufid), may Allah سبحانه وتعالى have mercy on him, said: “You must face the qiblah on a ship and pray standing if you are able; otherwise, (you may pray) sitting. If the ship turns, you should turn your face toward the qiblah. But if, after having initially faced it, the ship turns and you are unable to determine the qiblah due to the movement, then your initial direction suffices, and you continue to face wherever it turns. And if the qiblah becomes unclear to you in supererogatory prayers or after seeking its indications, then you should face the front of the ship and pray while it is ascending or descending and however it turns.”
Commentary #1