Sahih al-Bukhari — Shortening the Prayers (At-Taqseer) — Hadith No: 1107
Translation
Narrated Ibn `Abbas: Allah's Messenger (ﷺ) 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 (ﷺ) used to offer the Maghrib and the `Isha' prayers together on journeys