It is narrated from Ubayd bin Khalid al-Sulami (may Allah be pleased with him) that he (peace and blessings be upon him) said: "Sudden death is a seizure that brings grief."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6570
Rawh bin Ubadah narrated it from Shu'bah, from Mansur, from Tamim bin Salamah, from Ubayd, without doubt (about the narrator), and he attributed it to the Prophet (marfu'). Shu'bah said: This is how he narrated it to me, and another time he narrated it to me without attributing it to the Prophet.
Ibn Bashshar (may Allah have mercy on him) said: Muhammad bin Ja'far (may Allah have mercy on him) narrated to us; Shu'bah (may Allah have mercy on him) narrated the like of this hadith to us as mawquf (stopping at the Companion).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6571
Abdullah bin Ubayd bin Umayr said: I asked Sayyidah Aishah (may Allah be pleased with her) about sudden death: is it disliked? She said: "For what reason would it be disliked? I asked the Messenger of Allah (peace and blessings be upon him) about it, and he (peace and blessings be upon him) said: 'It is relief for the believer and a cause of grief for the wicked.'"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6572
Sayyiduna Abu Qatadah bin Rib'i (may Allah be pleased with him) narrates that a funeral passed by him (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Mustarih wa mustarah minhu" (This one is either at rest, or one from whom others are relieved). They said: "O Messenger of Allah, what is the one at rest (mustarih) and the one from whom others are relieved (mustarah minhu)?" He (peace and blessings be upon him) said: "The believing servant finds rest from the hardships and troubles of the world and attains the mercy of Allah; and the one who is a sinner, people, cities, trees and animals find relief from him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6574