It was narrated from Zainab bint Abi Salamah, from her mother, that a woman came to the Prophet (ﷺ) and asked him about her daughter whose husband had died and she was ill. He said: "One of you used to mourn for a year, then throw a piece of dung when a year had passed. Rather it (the mourning period) is four months and ten days."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ يَزِيدَ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ حُمَيْدِ بْنِ نَافِعٍ، عَنْ زَيْنَبَ بِنْتِ أَبِي سَلَمَةَ، عَنْ أُمِّهَا، أَنَّ امْرَأَةً، أَتَتِ النَّبِيَّ صلى الله عليه وسلم فَسَأَلَتْهُ عَنِ ابْنَتِهَا مَاتَ زَوْجُهَا وَهِيَ تَشْتَكِي قَالَ " قَدْ كَانَتْ إِحْدَاكُنَّ تَحِدُّ السَّنَةَ ثُمَّ تَرْمِي الْبَعْرَةَ عَلَى رَأْسِ الْحَوْلِ وَإِنَّمَا هِيَ أَرْبَعَةُ أَشْهُرٍ وَعَشْرًا " .
sunnah.com