Ash'ath (may Allah have mercy on him) said: I asked Ibrahim al-Nakha'i (may Allah have mercy on him): My hand is broken, and over it there is its cloth, its sticks and its splints, and sometimes I become junub? He said: Wipe over it with water, for Allah Almighty accepts a valid excuse.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1087