Abu Bakr was the closest friend of the Messenger of Allah ﷺ. He believed from the very beginning of the prophethood and spent his own wealth freeing persecuted slaves.
When the chiefs of Makkah plotted to kill the Prophet ﷺ, he emigrated to Madinah by Allah's permission — and chose Abu Bakr as his companion. To escape their pursuers, the two hid in a cave on Mount Thawr.
❝ HadithAbu Bakr said: while we were in the cave I looked up and saw the feet of our pursuers. I said, O Messenger of Allah, if one of them looks down at his feet he will see us. He said: O Abu Bakr, what do you think of two whose third is Allah?Sahih al-Bukhari 3653 · Sahih
The Quran preserved that moment for ever:
إِلَّا تَنصُرُوهُ فَقَدۡ نَصَرَهُ ٱللَّهُ إِذۡ أَخۡرَجَهُ ٱلَّذِينَ كَفَرُواْ ثَانِيَ ٱثۡنَيۡنِ إِذۡ هُمَا فِي ٱلۡغَارِ إِذۡ يَقُولُ لِصَٰحِبِهِۦ لَا تَحۡزَنۡ إِنَّ ٱللَّهَ مَعَنَاۖ فَأَنزَلَ ٱللَّهُ سَكِينَتَهُۥ عَلَيۡهِ وَأَيَّدَهُۥ بِجُنُودٖ لَّمۡ تَرَوۡهَا وَجَعَلَ كَلِمَةَ ٱلَّذِينَ كَفَرُواْ ٱلسُّفۡلَىٰۗ وَكَلِمَةُ ٱللَّهِ هِيَ ٱلۡعُلۡيَاۗ وَٱللَّهُ عَزِيزٌ حَكِيمٌ
“If you do not aid him [i.e., the Prophet (ﷺ)] - Allāh has already aided him when those who disbelieved had driven him out [of Makkah] as one of two, when they were in the cave and he [i.e., Muḥammad (ﷺ)] said to his companion, "Do not grieve; indeed Allāh is with us." And Allāh sent down His tranquility upon him and supported him with soldiers [i.e., angels] you did not see and made the word of those who disbelieved the lowest, while the word of Allāh - that is the highest. And Allāh is Exalted in Might and Wise.”
Surah At-Tawbah 9:40
Translation: Saheeh International (QuranEnc)
Abu Bakr's fear was not for himself but for the Prophet ﷺ. And the Prophet's ﷺ answer held a trust in Allah that remains a lesson for the whole ummah.