Musnad Abu Ya'la al-Mawsili 209:145

Abu Khaythama narrated to us, Shuja’ ibn al-Walid ibn Qays narrated to us, from ‘Ali ibn ‘Abd al-A’la, from Abu Sahl, from Massa al-Azdiyya, from Umm Salama, who said: The woman experiencing postpartum bleeding during the time of the Messenger of Allah (may Allah bless him and grant him peace) would sit for forty days. And we used to smear our faces with wars (a yellow plant) because of the melasma (dark spots).