Fiqh-us-Sunnah Volume 4, Funerals and Dhikr, Fiqh 4.025A.

Abu Daw’ud reported from ‘Ubaid ibn Khalid al-Sullami, a companion of the Prophet, peace be upon him, that once he narrated from ‘Ubaid and another time from the Prophet himself, peace be upon him, saying: “Being caught unawares by a sudden death is a grievous misfortune.”  This hadith has been reported by Abdullah ibn Mas’ud, Anas ibn Malik, Abu Hurairah and ‘Aishah, but all these narrations are weak for one or another reason. Al-Azdi says: This hadith has been reported through diverse chains of narrators, but none are reported on sound authority from the Prophet, peace be upon him.