Al-Kāfi

Hadith 456
iddah-waiting-periodmarriagedeathimam-ridhaahl-al-bayt
عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي نَصْرٍ عَنْ أَبِي الْحَسَنِ الرِّضَا ( عليه السلام ) قَالَ الْمُتَوَفَّى عَنْهَا زَوْجُهَا تَعْتَدُّ حِينَ يَبْلُغُهَا لِأَنَّهَا تُرِيدُ أَنْ تُحِدَّ عَلَيْهِ .
7. Ali ibn Ibrahim has narrated from his father from ibn abu Nasr who has said the following: “Abu al-Hassan, al-Rida’ (a.s.), has said, ‘A woman whose husband dies must begin counting her waiting period from the day the news reaches her as well as mourning for him.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī