It is the duty of a Muslim who has something which is to be given as a bequest not to have it for two nights without having his will written down regarding it.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ مَا حَقُّ امْرِئٍ مُسْلِمٍ لَهُ شَىْءٌ يُرِيدُ أَنْ يُوصِيَ فِيهِ يَبِيتُ لَيْلَتَيْنِ إِلاَّ وَوَصِيَّتُهُ مَكْتُوبَةٌ عِنْدَهُ  

This hadith has been narrated on the authority of 'Ubaidullah with the same chain of transmitters. but with a slight variation of words.  

عَنْ عُبَيْدِ اللَّهِ بِهَذَا الإِسْنَادِ غَيْرَ أَنَّهُمَا قَالاَ وَلَهُ شَىْءٌ يُوصِي فِيهِ وَلَمْ يَقُولاَ يُرِيدُ أَنْ يُوصِيَ فِيهِ  

A hadith like this have been narrated on the authority of Nafi', who based his narrations of the words of Ibn 'Umar but with a slight variation of words.  

عَنِ النَّبِيِّ ﷺ بِمِثْلِ حَدِيثِ عُبَيْدِ اللَّهِ وَقَالُوا جَمِيعًا لَهُ شَىْءٌ يُوصِي فِيهِ إِلاَّ فِي حَدِيثِ أَيُّوبَ فَإِنَّهُ قَالَ يُرِيدُ أَنْ يُوصِيَ فِيهِ كَرِوَايَةِ يَحْيَى عَنْ عُبَيْدِ اللَّهِ  

It is not proper for a Muslim who has got something to bequeathe to spend even three nights without having his will written down with him regarding it. 'Abdullah b. 'Umar (Allah be pleased with them) said: Ever since I heard Messenger of Allah ﷺ say this I have not spent a night without having my will (written) along with me.  

أَنَّهُ سَمِعَ رَسُولَ اللَّهِ ﷺ قَالَ مَا حَقُّ امْرِئٍ مُسْلِمٍ لَهُ شَىْءٌ يُوصِي فِيهِ يَبِيتُ ثَلاَثَ لَيَالٍ إِلاَّ وَوَصِيَّتُهُ عِنْدَهُ مَكْتُوبَةٌ قَالَ عَبْدُ اللَّهِ بْنُ عُمَرَ مَا مَرَّتْ عَلَىَّ لَيْلَةٌ مُنْذُ سَمِعْتُ رَسُولَ اللَّهِ ﷺ قَالَ ذَلِكَ إِلاَّ وَعِنْدِي وَصِيَّتِي  

This hadith has been narrated on the authority of Zuhri with the same chain of transmitters.  

عَنِ الزُّهْرِيِّ بِهَذَا الإِسْنَادِ نَحْوَ حَدِيثِ عَمْرِو بْنِ الْحَارِثِ