Salim bin 'Abdullah narrated from his father who said:"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

English translation · Jami' at-Tirmidhi