Hadhrat Abdullah bin Umar (radiyallahu anhuma) reports that Rasulullah (sallallahu alayhi wa sallam) said: “It is not permissible for any Muslim who has something to bequeath to stay for two nights without having his last will and testament written and kept ready with him. (Mishkaat).
Hadhrat Ibnu Umar (radiyallahu anhuma) says: “After hearing this from Rasulullah (sallallahu alayhi wasallam), I did not allow even one night to pass by me except that I had my wasiyyah written down.”