´Ibn 'Umar narrated that the Messenger of Allah (S.A.W) said:` "It is not right for a Muslim man to spend two nights, having what he would will, without having his will written with him."
Hadith Referenceسنن ترمذي / كتاب الوصايا عن رسول الله صلى الله عليه وسلم / 2118