Narrated Hudhaifah [may Allah be pleased with him]:
"We were sitting with the Prophet (ﷺ) and he said: 'I do not know how long I will be with you, so stick to the two after me,' and he signaled towards Abu Bakr and 'Umar." (JA)
English reference (JA): Vol. 1, Book 46, Hadith 3663 (JA)
Arabic reference (JA): Book 49, Hadith 4025 (JA)