Answered by Shaykh Faraz Rabbani
If one does a sajdah with the entire forehead covered, is the sajdah valid or what is the ruling regarding this? What if the forehead is partially covered? Does the thickness of the hat or turban material covering the forehead make a difference to the ruling?
It is valid to prostrate with some or all of one’s forehead covered, as mentioned in Maraqi al-Falah, and other texts. It is somewhat disliked, however, especially in the latter case, unless there is an excuse. It should be noted that in the Shafi`i school, it is a condition for the validity of one’s prostration that at least a little of the forehead be directly in contract during prostration.
In the Hanafi school, it is a condition for the prostration to be valid, however, that the prostration be on the area of the forehead, and that one be able to feel the ‘weight of the ground’ if one were to press down further, though it is not necessary to actually do so.