At the age of 35, a flood destroyed the Kaaba, and it needed to be rebuilt. Each tribe in Mecca was responsible for rebuilding a part of the Kaaba. The Black Stone, a holy, sacred object that was sent down from Paradise within the Kaaba was removed for the renovation and needed to be placed back into the Kaaba. The leaders of Mecca were in disagreement for 5 days, and blood was almost shed, trying to determine which clan would have the honor of placing the Black Stone back in its original place. They concluded that the next man that walked in would choose who would place the Black Stone back to its original place.
That person turned out to be Prophet Muhammad, peace be upon him. Instead of choosing a particular person or clan to place the Black Stone back in its original place, Prophet Muhammad, peace be upon him, asked for a cloth in which he placed the Black Stone in the center and had the leader of each clan hold a corner of the cloth and carry it back to the Kaaba together. Then Prophet Muhammad, peace be upon him, set the Back Stone with his two hands in its original place, and all the clans were satisfied.
This demonstrated and symbolized the future of Prophet Muhammad, peace be upon him, and how he would soon unify the Arab tribes under one banner of Islam, just like he unified them at this moment without any conflict or bloodshed. It also demonstrated and symbolized that Prophet Muhammad, peace be upon him, would be the one to unify the religion of Prophet Abraham, peace be upon him, after it was destroyed.