Sahih al-Bukhari, Volume 7, Book 63, Hadith 253 (USC-MSA) ⓘ
Narrated Um 'Atiyya: We were forbidden to mourn for more than three days except for a husband.
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا بِشْرٌ، حَدَّثَنَا سَلَمَةُ بْنُ عَلْقَمَةَ، عَنْ مُحَمَّدِ بْنِ سِيرِينَ، قَالَتْ أُمُّ عَطِيَّةَ نُهِينَا أَنْ نُحِدَّ أَكْثَرَ مِنْ ثَلاَثٍ إِلاَّ بِزَوْجٍ.
also referenced under: Book 68, Hadith 85 (In-Book) & Hadith 5340 (DarusSalam)