Musannaf Ibn Abi Shayba 1:1660

Marwan ibn Mu'awiyah narrated to us, from 'Awf, from Abu Raja', who said: Imran ibn Husayn narrated to us that the Messenger of Allah (may Allah bless him and grant him peace) was on a journey and led the people in prayer. Then, there was a man who had isolated himself to the side of the people. The Messenger of Allah (may Allah bless him and grant him peace) said: "What is the matter with you that you did not pray with the people?" He said: "I have become in a state of major ritual impurity (janaba), O Messenger of Allah, and there is no water." The Messenger of Allah (may Allah bless him and grant him peace) said: "You must use the earth (al-sa'id), for it is sufficient for you."