‘Abdullāh ibn ‘Umar narrated that Allāh’s Messenger ﷺ said:

ما حقُّ امرئ مسلم له شيء يوصي فيه، يَبيتُ ليلتين إلا ووصيتُه مكتوبة عنده

“It is the duty of every Muslim who has any affair that ought to be recorded in a will to not allow two nights to pass without having his last will and testament written and kept with him.”^[1]

Imām ‘Abdul-‘Azīz ibn Bāz said:

“It is legislated for the believer to have a will for what is upon them from debts and rights of others so that they are transferred. Especially if there are no legal documents which could cause the rights of others to be lost. If that is the case, then it is obligatory to have a will so that the rights are fulfilled.”^[2]

Footnotes:

[1] Ṣaḥīḥ al-Bukhārī (no. 2738) and Ṣaḥīḥ Muslim (no. 1627)

[2] From the Shaykh’s official website