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.
Hadith Referenceصحيح البخاري / كتاب تقصير الصلاة / 1107
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة