Abu Uthman al-Nahdi (may Allah have mercy on him) said that when Sa'id bin Zayd and Usamah bin Zayd (may Allah be pleased with them both) were in haste on a journey, they would combine Zuhr and Asr, and Maghrib and Isha.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5540