Is it permissible to prostrate on a soft surface, such as a blanket, during prayer, or must prostration be on a firm surface?

It is permissible to prostrate on a smooth, soft surface such as a blanket or similar, provided that the worshiper is able to firmly place his forehead and nose during prostration. What is forbidden is prostrating on something so soft that the face sinks into it and does not become stable. The fundamental principle of prostration is that it should be on the earth or what is considered to be like it, something upon which the worshiper can feel its volume and upon which his forehead can rest firmly. If the prayer rug is firm and stable and does not prevent the forehead from being firmly placed, then there is no objection to prostrating on it.