Sahih Muslim Book - 25, Hadith - 4207

حَدَّثَنَا هَارُونُ بْنُ مَعْرُوفٍ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ وَهْبٍ أَخْبَرَنِى عَمْرٌو - وَهْوَ ابْنُ الْحَارِثِ - عَنِ ابْنِ شِهَابٍ عَنْ سَالِمٍ عَنْ أَبِيهِ أَنَّهُ سَمِعَ رَسُولَ اللَّهِ -صلى الله عليه وسلم- قَالَ « مَا حَقُّ امْرِئٍ مُسْلِمٍ لَهُ شَىْءٌ يُوصِى فِيهِ يَبِيتُ ثَلاَثَ لَيَالٍ إِلاَّ وَوَصِيَّتُهُ عِنْدَهُ مَكْتُوبَةٌ ». قَالَ عَبْدُ اللَّهِ بْنُ عُمَرَ مَا مَرَّتْ عَلَىَّ لَيْلَةٌ مُنْذُ سَمِعْتُ رَسُولَ اللَّهِ -صلى الله عليه وسلم- قَالَ ذَلِكَ إِلاَّ وَعِنْدِى وَصِيَّتِى.

It was narrated from Salim, from his father, that he heard the Messenger of Allah (s.a.w) say: "It is not right for a Muslim man who has anything to be bequeathed to stay for three nights without having his will written down with him." 'Abdullah bin 'Umar said: "Since I heard the Messenger of Allah (s.a.w) say that, no night passed but I had my will with me."