Muwatta Malik, Book 29, Hadith 104 (USC-MSA) ⓘ

Yahya related to me from Malik from Nafi from Safiyya bint Abi Ubayd from A'isha and Hafsa, the wives of the Prophet, may Allah bless him and grant him peace, that the Messenger of Allah, may Allah bless him and grant him peace, said, "It is not halal for a woman in mourning for someone who has died, if she trusts in Allah and the Last Day, to abstain from adornment for more than three nights, except for a husband."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ صَفِيَّةَ بِنْتِ أَبِي عُبَيْدٍ، عَنْ عَائِشَةَ، وَحَفْصَةَ، زَوْجَىِ النَّبِيِّ صلى الله عليه وسلم أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ لاَ يَحِلُّ لاِمْرَأَةٍ تُؤْمِنُ