Musnad Ahmad 1153:30

Isma'il narrated to us, from Ibn 'Awn, from Ibrahim, from al-Aswad, who said: They mentioned in the presence of 'Aishah that 'Ali was a legatee (wasi). She said: "When did he bequeath to him? For I was leaning him against my chest," or she said: "in my lap, and he called for the basin, then he slumped in my lap, and I did not perceive that he had died. So when did he bequeath to him?"