The Messenger of Allah ﷺ as saying: It is the duty of a Muslim man who has something which is to be given as bequest not to have it for two nights without having his will written regarding it.
عَنْ رَسُولِ اللَّهِ ﷺ قَالَ مَا حَقُّ امْرِئٍ مُسْلِمٍ لَهُ شَىْءٌ يُوصِي فِيهِ يَبِيتُ لَيْلَتَيْنِ إِلاَّ وَوَصِيَّتُهُ مَكْتُوبَةٌ عِنْدَهُ