al-Aswad bin Yazid الأسود بن يزيد بن قيس النخعي · The Book of Wills

It was mentioned before A'isha that will had been made (by the Holy Prophet) in favour of 'Ali (as the Prophet's first caliph), whereupon she said: When did he make will in his favour? I had been providing support to him (to the Holy Prophet) with my chest (or with my lap). He asked for a tray, when he fell in my lap (relaxing his body), and I did not realise that he had breathed his last. When did he…

"The Messenger of Allah said: 'It is not befitting for a Muslim who has anything concerning which a will should be made, to abide for two nights without having a written will with him.'"

"It is not befitting for a Muslim who has anything concerning which a will should be made, to abide for two nights without having a written will with him."

(The same) was narrated from Ibn 'Awn, from Nafi', from Ibn 'Umar.