مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4155
Musnad of Abdullah bin Mas'ood
It was narrated from Abu Wa'il, from ‘Abdullah, and I think he attributed it to the Prophet (ﷺ) that he said: "Ahead of the Hour there will be days of harj, days in which knowledge will disappear and ignorance will prevail." Abu Moosa said: Harj in the language of the Abyssinians means killing.
Musnad Ahmad 4183Its isnad is saheeh, al-Bukhari (7066)]