Musnad Abu Ya'la al-Mawsili 225:3

Zuhayr narrated to us, Mansur ibn Salamah al-Khuza'i narrated to us, Malik informed us, from Abdullah ibn Abi Bakr, from Humayd ibn Nafi', from Zaynab bint Umm Salamah, that she informed him, saying: I entered upon Zaynab bint Jahsh when her brother died. She called for perfume and applied some of it. Then she said: "By Allah, I have no need for perfume, except that I heard the Messenger of Allah (peace and blessings of Allah be upon him) saying upon the pulpit: 'It is not lawful for a woman who believes in Allah and the Last Day to observe mourning for a dead person for more than three nights, except for a husband, [for whom it is] four months and ten [days].'"