It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) said concerning the menstruating woman: "She should wash only the part (of her garment) that the blood has touched, and not wash the whole garment."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20268