Narrated Umar ibn al-Khattab (R.A.): The Messenger of Allah (Sallalaho Alayhe Wa Alehi Wassalam) commanded us one day to give sadaqah. At that time I had some property. I said: Today I shall surpass Abu Bakr if I surpass him any day. I, therefore, brought half my property. The Messenger of Allah (Sallalaho Alayhe Wa Alehi Wassalam) asked: What did you leave for your family? I replied: The same amount. 

Abu Bakr brought all that he had with him. The Messenger of Allah (Sallalaho Alayhe Wa Alehi Wassalam) asked him: What did you leave for your family? He replied: I left Allah and His Messenger for them.

I said: I shall never compete you in anything.

[Abu Dawud] Also recorded by At-Tirmidhi.


Many of the scholars of Tafsir have mentioned that the following Ayats were revealed about Abu Bakr As-Siddiq may Allah be pleased with him.
“But the righteous one will avoid it (Hell) – [He] who gives [from] his wealth to purify himself. And not [giving] for anyone who has [done him] a favor to be rewarded. But only seeking the countenance of his Lord, Most High. [92:17-20] 

And Allah's Messenger (Sallalaho Alayhe Wa Alehi Wassalam)said, "No doubt, I am indebted to Abu Bakr more than to anybody else regarding both his companionship and his wealth. 
[Al-Bukhari and Muslim]