It was narrated that Hudhaifah bin Yaman said:
"The Messenger of Allah (ﷺ) said: 'I do not know how long I will stay among you, so follow the example of these two after I am gone,' and he pointed to Abu Bakr and `Umar." (ID)
English reference (ID): Vol. 1, Book 1, Hadith 97 (ID)
Arabic reference (ID): Book 1, Hadith 102 (ID)