Musannaf Ibn Abi Shayba 1:1480

Abbad ibn al-Awwam narrated to us, from Sa’id, from Abu Ma’shar, from Ibrahim, regarding a man who prays while there is *hubun* (pustules/abscesses) on his garment: He said, "He does not wash it until it heals. When it heals, he washes it." He said, "And I have seen Ibrahim praying while there was pus from *hubun* that he had on his garment."