The Messenger of Allah (may Allah's peace and blessings be upon him) saw a person sitting …

The Prophet (may Allah's peace and blessings be upon him) led his Companions in the Fajr prayer. When he finished the prayer, he noticed a man that had not prayed with them. Out of his remarkable gentleness and good call to Allah, the Almighty, he did not rebuke the man for having failed to attend the congregational prayer until he could know the reason behind this. So, he asked the man: “O so-and-so, what prevented you from praying with the congregation?” The man clarified his excuse, according to his reasoning. He said that he was in a state of ritual impurity and had no water; that is why he delayed the prayer until he could find water and purify himself therewith. Thereupon, the Prophet (may Allah's peace and blessings be upon him) informed him that Allah, the Almighty, out of His kindness, provided a replacement for water when it comes to purification; and that is clean earth. He told him to use it instead of water, which was unavailable.