A woman of Banu Abd al-Ashhal (may Allah be pleased with her) said: I said: O Messenger of Allah (peace and blessings be upon him), between me and the mosque there is a filthy path; what should we do when it rains? He (peace and blessings be upon him) said: "Is there not a path after it that is cleaner than it?" I said: Indeed there is. He (peace and blessings be upon him) said: "This is in exchange for that."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4268