Sayyidah Umm Salamah (may Allah be pleased with her) narrates: One of us women would menstruate in her clothes; then, when the day of her purity came, she would wash whatever had got on that garment and then pray in that same garment. And today your state is such that one of you women keeps her maidservant reserved for this task alone on the day of her purity, so that she may wash her (menstrual) clothes.
Imam al-Tabarani recorded it in al-Mu'jam al-Awsat, and its narrators have been declared trustworthy.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1556