عن عبد الله بن عمر رضي الله عنهما مرفوعاً: «ما حق امرئ مسلم له شيء يوصي فيه؛ يبيت ليلتين إلا ووصيته مكتوبة عنده».
زاد مسلم: قال ابن عمر: «ما مرت علي ليلة منذ سمعت رسول الله صلى الله عليه وسلم يقول ذلك، إلا وعندي وصيتي». [صحيح] - [متفق عليه] المزيــد ...
‘Abdullāh ibn ‘Umar (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "It is not befitting for a Muslim who has anything concerning which a will should be made, to abide for two nights without having his will with him."
Imām Muslim added that ibn ‘Umar said: "Not one night passed by me since I heard the Messenger of Allah (may Allah's peace and blessings be upon him) mention this, except that I had a written will with me.'' Sahih/Authentic. - [Al-Bukhari and Muslim]
It is not correct or proper for someone who possesses something to be bequeathed or clarified, to neglect it for a long time. Rather, one should record and write it as soon as possible. The longest period of time permitted for someone not to write a will, is one or two nights. That is why Ibn ‘Umar (may Allah be pleased with him) after hearing this prophetic advice used to check his will every night. He did so as to adhere to Prophet's command and state the rights.
A will is of two types.
1. Recommended will that one writes regarding voluntary deeds and acts of worship.
2. Obligatory will that one makes regarding the mandatory rights, which have no proofs to confirm them after one's death. This is based on the juristic rule that what is required for the fulfillment of an obligation is obligatory. Ibn Daqīq El-Eid stated that this Hadīth addresses the obligatory types of will.