From Sahih Muslim (Hadith 3729):
Zainab bint Umm Salama (Allah be pleased with her) reported that a relative of Umm Habiba (Allah he pleased with her) died. She sent for a yellow (perfume) and applied that to her forearm and said:I, am doing it, for I have heard Allah's Messenger (ﷺ) saying: It is not permissible for a woman believing in Allah and the Hereafter to mourn beyond three days except the husband (for whom she can mourn) for four months and ten days
Reference: Muslim 3729