Sayyidah Aishah (may Allah be pleased with her) said: I used to comb the hair of the Messenger of Allah (peace and blessings be upon him) while I was menstruating. (b) Imam al-Shafi'i (may Allah have mercy on him) took as evidence the order of the Prophet (peace and blessings be upon him) concerning the menstrual blood of a menstruating woman that gets on her garment, that "it should be washed," and he (peace and blessings be upon him) did not order the whole garment to be washed. There is no doubt about the sweat in it. This hadith has already passed in several places.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 882