What is the ruling on the prayer of one who moved his head during prostration to enable himself to prostrate with the largest possible area of his nose and forehead, then the Imam rose before he became still, knowing that he prostrated on his nose and forehead during the movement and recited the tasbeeh? And is momentary stillness with tasbeeh sufficient for the congregant? And what is the ruling on slight head movement resulting from the thickness of the prayer rug?

Tranquillity (طمأنينة) is a pillar of prayer in bowing (rukūʿ), standing erect after bowing (iʿtidāl), prostrating (sujūd), and sitting between the two prostrations. The minimum level of tranquillity is the stillness of the limbs for the duration of saying "Subhan Allah" (Glory be to Allah). The worshipper must press down on the place of prostration until their forehead is stable. If one prostrates on cotton or grass, one must press down until it compresses. If there is no stillness between the movement of descending into prostration and the movement of rising from it, the prostration is not valid. If the prayer rug is thick and light such that it compresses, it is necessary to press down until compression occurs.