Prohibition to prostrate on stone floors (outside the Temple)
Toward the end of the second century, the Rabbis teachers in Jerusalem, relying on "Ye shall make you no idols nor graven image, neither rear you up a standing image, neither shall ye set up any image of stone in your land, to bow down unto it: for I am the LORD your God." (Leviticus 26:1), took hishtakhaweh as meaning to spread oneself, and taught that it was forbidden outside of the Temple to prostrate oneself upon stone pavement (Sifra, Behar, end; Megilah 22b), in the Land of Israel. The custom of partial prostration (qida) in the Shemoneh Esrei and full prostration (hishtakhaweh) in Tachnun become merely a symbolic bow, or resting the head on the hands.
The prostrations continued in Babylon (see “Prostration after the Destruction of the Temple” above). In Babylon, in deference to the custom in Israel, the Sages require the use of a prayer mat, cloth or some other object so as to avoid bowing down directly on stone.
The custom of the Land of Israel (symbolic prostrations) gradually found its way into Babylon and the other lands of the diaspora. It was retained only through the use of a prayer mat, during the high holiday services.