Sahih Muslim Book 4, Hadith Number 1324.

Chapter : The severity (of punishment) in missing the ‘Asr prayer.

‘Umara b. Ruwaiba is reported to have said on the authority of his father: I heard the Messenger of Allah (may peace be upon him) saying: He who observed prayer before the rising of the son and its setting, i.e. the dawn prayer and the afternoon prayer, would not cater the (Hell) fire. A person belonging to Basra said to him: Did you yourself bear it from the Messenger of Allah (may peace be upon him)? He said: Yes. The person (from Basra) said: I bear witness that I heard it from the Messenger of Allah (may peace be upon him); my ears heard it and my heart retained it.