Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.
Wa alaikum assalam wa rahmatullahi wa barakatuh.
As to what follows:
A group of scholars, including Imam Shafi`i (may Allah have mercy on him), opined that it is not permissible to prostrate while there is a connected material on the one praying, such as his turban or garment [coming between him and the place of prostration]. They evidenced this by the hadith of Khabbab bin al-Aratt (may Allah be pleased with him) when he said, “We came to the Messenger of Allah (peace be upon him), and complained to him about praying on the extremely heated ground (or sand), but he paid no heed to us.” [Muslim (619)]
Thus, they said that it is obligatory for the body parts of the one praying to come in contact directly with the place of prostration.
The majority of scholars from the Tabi`un, jurists of various Madh'habs and others, differed with this opinion. They opined that it is not obligatory for the body parts of the one praying to come in contact directly with the place of prostration. They evidenced this with what was narrated by Bakr bin `Abdullah, on the authority of Anas (may Allah be pleased with him) when he said, “We used to pray with the Prophet (peace be upon him) and some of us used to place the ends of their clothes at the place of prostration because of scorching heat.” [Bukhari (385) and Muslim (620)]
What is closest to being correct from the gathered evidences, is that if there is no pressing need, it is better not to prostrate on something [that will come between the one praying and the ground]. And Allah knows best.
Dr. Khalid al-Muslih
13 / 6 / 1427 AH