Here is the quoatation from the blog Alhamdulillah:
In the Name of Allah; the Merciful, the Compassionate.Make your will while you still can. This sinner has seen examples where this lack of action has resulted in much damage.
Abdullah ibn Umar (may Allah be pleased with him) narrated:
Allah's Messenger [peace and blessings be upon him] said: "It is not permissible for any Muslim who has something to will, to stay for two nights without having his last will and testament written and kept ready with him."Sahih al Bukhari, Hadeeth 1, Vol. 4.