كتاب الوصية
Read the English translation first, with the original Arabic directly underneath.
Ibn Umar (Allah be pleased with them) reported Allah's Messenger (ﷺ) as saying:
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.
مَا حَقُّ امْرِئٍ مُسْلِمٍ لَهُ شَىْءٌ يُرِيدُ أَنْ يُوصِيَ فِيهِ يَبِيتُ لَيْلَتَيْنِ إِلاَّ وَوَصِيَّتُهُ مَكْتُوبَةٌ عِنْدَهُ