It is a Bid'ah to avoid stepping on places of prostration
23-3-2014 | IslamWeb
Question:
Assalamu alaikum, I read in some places that when folding a prayer mat, one should be careful that the part where one stands and the part where one does Sajdah should not contact with each other. Is there any reference to it? Also, when we walk in a mosque, should we avoid stepping on places where the Sajdah is made? I mean, it is really hard to avoid stepping on prostration places when crossing rows (I've tried). Thank you.
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His slave and Messenger.
It is not permissible for anyone to oblige people to do what Allaah The Almighty did not command them to do in His Book nor the Prophet commanded them to do in his Sunnah. Avoiding the places of prostration when walking in the mosque or when folding a prayer mat has no basis and Allaah The Almighty did not command this in His Book.
Furthermore, nor was it reported that the Prophet prevented his Companions from walking on the places of prostration in the mosque and he did not prevent or warn them against what you mentioned about folding a prayer mat. Rather, they were not keen on praying on a mat at all.
Shaykh Ibn Taymiyyah 
was asked (as reported in Majmoo’ Al-Fataawa) about spreading a mat in the mosque and praying on it and if this is an innovation or not. He replied: “Praise be to Allaah. With regards to a person praying on a mat in a way where he is keen on doing so, then this is not the Sunnah of the Salaf (righteous predecessors) from among the Muhaajireen (emigrants from Makkah) and the Ansaar (supporters in Al-Madeenah) at the time of the Prophet and those after them from among the Taabi’is (successors of the Prophet's Companions). Rather, they used to pray in his mosque directly on the ground and none of them used a prayer mat that is specifically reserved for prayers. It was reported that when Abdur-Rahmaan ibn Mahdi came to Al-Madeenah, he spread a prayer mat to pray on; so Imaam Maalik ordered that he be detained and the people told him: “This is Abdur-Rahmaan ibn Mahdi”. Imaam Maalik said: “Did you not know that spreading a prayer mat in our mosque is an innovation?”
Allaah Knows best.