Al-Kāfi - Volume 6 > Waiting period of a Widow whose Husband is Absent
Hadith #7

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’, ‘Alayhi al-Salam, 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.’”