Shortening the Prayers (At-Taqseer)

Bukhari :: Book 2 :: Volume 20 :: Hadith 209

Narrated Salim's father:

The Prophet used to offer the Maghrib and Isha' prayers together whenever he was in a hurry on a journey.

Narrated Ibn Abbas: Allah's Apostle used to offer the Zuhr and 'Asr prayers together on journeys, and also used to offer the Maghrib and 'Isha' prayers together.

Narrated Anas bin Malik: The Prophet used to offer the Maghrib and the 'Isha' prayers together on journeys.