Is it permissible to prostrate on an elevated object placed before oneself, such as a cushion or stone?
Chapter on the Times When Prayer is Prohibited
Al-Mughni
Book of Prayer
Primary text
It is permissible to place a cushion, something elevated, or to prostrate on a mound or stone if one cannot lower their face further than that level. This is based on the principle that one has performed the maximum possible descent, thus fulfilling the obligation, similar to when one merely points.
Supporting text
Some scholars rule that placing something high to prostrate upon is invalid. A narration from Ibn Mas'ud, Ibn Umar, Jabir, and Anas states that one should only point (Ima') and not raise anything to the face for prostration. This view is held by 'Ata, Malik, and ath-Thawri. Ahmad narrated that whichever action is performed, pointing or prostrating on a raised object like an elbow rest, there is no harm, though pointing is preferred over raising an object.