The clogs of today are different than the ones used in the time of our Master, the Prophet. They were shoes that had leather bottoms, and the tops were open and had a strap. Rasûlullah and the Ashâb al-kirâm performed namâz with the clogs they wore in the streets. Their clogs were clean, and the Masjid an-Nabî’s ground was sand. No one entered with dirty clogs. 
In a hadîth ash-sharîf, it was said, “Perform namâz with your clogs so that you won’t resemble the Jews.”