Sahih al-Bukhari, Volume 9, Book 92, Hadith 374 (USC-MSA) ⓘ

Narrated Anas bin Malik: That he heard `Umar speaking while standing on the pulpit of the Prophet in the morning (following the death of the Prophet), when the people had sworn allegiance to Abu Bakr. He said the Tashah-hud before Abu Bakr, and said, "Amma Ba'du (then after) Allah has chosen for his Apostle what is with Him (Paradise) rather than what is with you (the world). This is that Book (Qur'an) with which Allah guided your Apostle, so stick to it, for then you will be guided on the right path as Allah guided His Apostle with it."

حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، أَخْبَرَنِي أَنَسُ بْنُ مَالِكٍ، أَنَّهُ سَمِعَ عُمَرَ الْغَدَ، حِينَ بَايَعَ الْمُسْلِمُونَ أَبَا بَكْرٍ، وَاسْتَوَى عَلَى مِنْبَرِ رَسُولِ اللَّهِ صلى الله عليه وسلم تَشَهَّدَ قَبْلَ أَبِي بَكْرٍ فَقَالَ أَمَّا بَعْدُ فَاخْتَارَ اللَّهُ لِرَسُولِهِ صلى الله عليه وسلم الَّذِي عِنْدَهُ عَلَى الَّذِي عِنْدَكُمْ، وَهَذَا الْكِتَابُ الَّذِي هَدَى اللَّهُ بِهِ رَسُولَكُمْ فَخُذُوا بِهِ تَهْتَدُوا وَإِنَّمَا هَدَى اللَّهُ بِهِ رَسُولَهُ‏.‏