Read all Ahadith in the book of the merits of the companions by sahih al muslim

Anas b. Malik reported that Abu Bakr Siddiq reported him thus: I saw the feet of the polytheists very close to us as we were in the cave. I said: Allah's Messenger, if one amongst them were to see at his feet he would have surely seen us. Thereupon he said: Abu Bakr, what can befall two who have Allah as the third One with them.

Abu Sa'id reported that Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) sat on the pulpit and said: Allah gave a choice to His servant that he may opt the beauties of the world or that which is with Him and the servant chose that which was with Him. Thereupon Abu Bakr wept and he wept bitterly and said: Let our fathers and our mothers be taken as ransom for you. It was Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) who had been given the choice and Abu Bakr knew it better than us, and Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) is reported to have said: Behold, of all people the most generous toward me in regard to his companionship and his property was Abu Bakr and were I to choose anyone as my bosom friend, I would have chosen Abu Bakr as my dear friend, but (for him) I cherish Islamic brotherliness and love. There shall be left open no window in the mosque except Abu Bakr's window.

This hadith has been narrated on the authority of Abu Sa'id Khudri through another chain of transmitters.

Abdullah b. Mas'ud reported Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) as saying: If I were to choose a bosom friend I would have definitely chosen Abu Bakr as my bosom friend, but he is my brother and my companion and Allah, the Exalted and Gliorious. has taken your brother and companion (meaning Prophet himself) as a friend

Abdullah reported Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) as saying: If I were to choose from my Umma anyone as my bosom friend, I would have chosen Abu Bakr.

Abdullah reported Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) as saying: If I were to choose as my bosom friend I would have chosen the son of Abu Quhafa (Abu Bakr) as my bosom friend.

Abdullah reported Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) as saying: If I were to choose amongst the people of earth someone as my bosom friend, I would have chosen the son of Abu Quhafa as my friends but God has taken your companion as a friend.

This hadith has been narrated through another chain of transmitters and the one narrated on the authority of Abdullah (the words are): Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) is reported to have said: Behold I am free from the dependence of all bosom friends and if I were to choose anyone as bosom friend I would have taken Abu Bakr as my bosom friend. Allah has taken your companion as a friend.

Amr b. al-'As reported that Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) sent him in command of the army despatched to Dhat-as-Salasil. When 'Amr b. al-'As came back to the Prophet ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) he said: Who amongst people are dearest to you? He said: A'isha. He then said: Who amongst men? He said: Her father, and I said: And who next? He said: Umar. He then enumerated some other men.

Ibn Abu Mulaika reported: I heard `A'isha as saying and she was asked as to whom Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) would have nominated as his successor if he had to nominate one at all. She said: Abu Bakr. It was said to her: Then whom after Abu Bakr? She said: `Umar. It was said to her. Then whom after `Umar? She said: Abu `Ubaida b. al-Jarrah, and then she kept quiet at this.