Sahih Muslim Book 4, Hadith Number 1300.

Chapter : Desirability of observing the noon prayer at the earlier hour (of times prescribed for it) when there is no intense heat.

Anas b. Malik reported: We used to offer the afternoon prayer (at such a time) that a person would go to Bani ‘Amr b. Auf and he would find them busy offering the afternoon prayer.