"It was said to 'Umar bin Al-Khattab: 'Perhaps you should endorse your successor.' He said: 'If I appoint a successor, then indeed Abu Bakr appointed a successor. And if I do not appoint a successor, the Messenger of Allah(s.a.w) did not appoint a successor."'
Jami` at-Tirmidhi Book 33, Hadith 68
← Previous Hadith "I was with Abu Bakrah under the Minbar of Ibn 'Amir while he was giving a Khutbah wearing a fine garment. Abu Bilal said: 'Look at our Amir wearing clothes of wickedness!' So Abu Bakrah said: Be quiet! I heard the Messenger of Allah(s.a.w) saying: "Whoever insults Allah's Sultan on the earth, Allah disgraces him."

Jami` at-Tirmidhi Book 33, Hadith 67 Next Hadith → "Safinah narrated to me, he said: 'The Messenger of Allah(s.a.w) said: "Al-Khilafah will be in my Ummah for thirty years, then there will be monarchy after that."' Then Safinah said to me: 'Count the Khilafah of Abu Bakr,' then he said: 'Count the Khilafah of 'Umar and the Khilafah of 'Uthman.' Then he said to me: 'Count the Khilafah of 'Ali."' He said: "So we found that they add up to thirty years." Sa'eed said: "I said to him: 'Banu Umaiyyah claim that the Khilafah is among them.' He said: 'Banu Az-Zarqa' lie, rather they are a monarchy, among the worst of monarchies."'

Jami` at-Tirmidhi Book 33, Hadith 69