Musnad Ahmad 1479

Hisham narrated, from his father, from Sa"d, that The Prophet (ﷺ) entered upon him to visit him when he was sick. He said: “O Messenger of Allah, shall bequeath all of my wealth (to charity)?” He said: “No." He said: “Half?” He said: "No." He said: “One third?” He said: "One third, and one third is a lot.”