أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا سُفْيَانُ، عَنِ الزُّهْرِيِّ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ لاَ يَحِلُّ لاِمْرَأَةٍ تَحِدُّ عَلَى مَيِّتٍ أَكْثَرَ مِنْ ثَلاَثٍ إِلاَّ عَلَى زَوْجِهَا ‏"‏ ‏.‏

It was narrated from 'Aishah that the Messenger of Allah said: "It is not permissible for a woman to mourn for anyone who dies for more than three days, except for her husband." Translation Not Available

Book Ref: Sunan An Nisai Book 27 Hadith 3525
Web Ref:  Sunan An Nisai Vol 4 Book 27 Hadith 3555