A hadith like this is transmitted on the authority of Nafi'.
Sahih Muslim Book 18, Hadith 81
← Previous Hadith It is not permissible for a woman believing in Allah and the Hereafter (or believing in Allah and His Messenger) that she should observe mourning for the dead beyond three days except in case of her husband.

Sahih Muslim Book 18, Hadith 80 Next Hadith → " She should abstain from adorning herself (in case of the death of her husband) for four months and ten days."

Sahih Muslim Book 18, Hadith 82