Abu Sa'id al-Khudri reported that he went to the Messenger of Allah ﷺ and found him observing prayer on a mat and prostrating on that.
The Prophet Muhammad's example shows us that even though he was the leader of his people, he still humbled himself before Allah in prayer by using a simple mat instead of something more luxurious or ornate. This teaches us to be humble in all aspects of life and not let pride get in the way of our relationship with Allah. It also reminds us that material possessions are not important when it comes to worshiping God; rather, what matters most is sincerity and humility in our hearts towards Him.