He replied...
He replied: "Prostration is only permissible on earth or what has grown from the earth, except what is eaten and worn." I then asked Him: "May my soul be ransomed for you, what is the cause of that?" He replied: "Because prostration is the submission to the Exalted and Glorious Lord and so it should not be on what is eaten or worn because the world is a slave to what they eat or wear; and the prostrator in his act of prostration, worshipping the Exalted and Glorious Lord, thus he should not put his forehead on the impudent and worldly things whilst undergoing prostration.
Thus, the prostration that is done on earth is better, because it is a sign of humility and submission for the Exalted Lord." The above-mentioned tradition clearly proves why prostration on earth ought to be considered, and that is because of the fact that it is more in agreement with showing humility before the one and only God. One other question that is normally raised is that why the Shia limit their prostration on the earth and only particular plants and why not all the plants.
In response to this, we say that because the principles of worship have got to be from the sacred Islamic law, then the conditions and the details pertaining to the worship ought to be emulated by the honorable Prophet's speech and action, because the Holy Prophet is an ideal for the pious men according to the holy Quran.
At this point, let us mention some of the Islamic narrations that clearly explain the Holy Prophet's practice and prove that He prostrated both on earth as well as particular plants such as the 'Haseer' (reed mat) just as the Shia believe in doing so. A group of Muslim narrators in their authentic books mention that the holy prophet described the earth as being his place for prostration.
"The earth was made for me as a place for prostration and the cause of purification." The word 'made' in this particular narration means legislated, which clearly shows that the matter is of divine consideration, not to mention a commandment from the Lord for the followers of Islamic religion, and in this way the legality of prostration on sand, stones and other parts that constitute the surface of the earth is already proven.
(Everything that the Holy Prophet uttered was direct revelation 'wahy' from the Lord of the worlds.) Another group of narrations show that the honorable prophet ordered the believers to place their foreheads on sand while prostrating.