Mishkat al-Masabih 3329
Umm Salama told that a woman came to the Prophet and said:
"Messenger of God, my daughter’s husband has died and her eye is troubling her, so may we apply collyrium to it?” He said “No” twice or thrice, saying only “No” all the time. Then he said, “It is only four months and ten days, whereas in the pre-Islamic period none of you threw away the piece of dung till a year had passed.”* 
* The reference is to a pre-Islamic custom by which a widow threw a piece of dung when her idda period came to an end. Cf. Lane, Lexicon and Taj al-'arus ; Mirqat , 3:513 f.
  
(Bukhari and Muslim.)
وَعَن أُمِّ سلمةَ قَالَتْ: جَاءَتِ امْرَأَةٌ إِلَى النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَتْ: يَا رَسُولَ اللَّهِ إِنَّ ابْنَتِي تُوُفِّيَ عَنْهَا زَوْجُهَا وَقَدِ اشْتَكَتْ عَيْنُهَا أَفَنَكْحُلُهَا؟ فَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «لَا» مَرَّتَيْنِ أَوْ ثَلَاثًا كُلُّ ذَلِكَ يَقُولُ: «لَا» قَالَ: «إِنَّمَا هِيَ أَرْبَعَةُ أَشْهُرٍ وعشرٌ وَقد كَانَت إِحْدَاهُنَّ فِي الجاهليَّةِ تَرْمِي بِالْبَعْرَةِ عَلَى رَأْسِ الْحَوْلِ»