Salim narrates from his father that the Prophet Muhammad (peace be upon him) said: "It is not permissible for a Muslim person that three days pass (and he has not written his will); his will should be with him."
Hadith Referenceصحیح ابن حبان / كتاب الوصية / 6025
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح: ق - انظر ما قبله.فضيلة الشيخ العلّامة شُعيب الأرناؤوطحديث صحيح