Sahih Al Bukhari Hadith Number 1106

Narrated Salim’s father: The Prophet (peace be upon him) used to offer the Maghrib and `Isha’ prayers together whenever he was in a hurry on a journey.

18  Shortening the Prayers (At-Taqseer)
Hadith number 1106
Volume no 2
Chapter: 13 (To offer Maghrib and “Isha” prayers together on a journey)