Sunan an-Nasa'i 808

Muhammad ibn Umar ibn Ali ibn Muqaddam narrated to us: Yusuf ibn Yaqub narrated to us: At-Taymi informed me from Abu Mijlaz, from Qays ibn Ubad, who said: While I was in the mosque in the front row, a man behind me pulled me aside and took my place. By Allah, I could not concentrate on my prayer. When he finished, I saw that it was Ubayy ibn Ka‘b. He said, 'Young man, may Allah spare you any harm. This is an instruction the Prophet ﷺ gave us: that we should stand directly behind him.' Then he faced the qiblah and said three times, 'By the Lord of the Ka‘bah, the people of authority have perished!' Then he said, 'By Allah, I do not grieve for them, but I grieve for those whom they have led astray.' I asked, 'Abu Yaqub, whom do you mean by the people of authority?' He said, 'The rulers.'