It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings of Allah be upon him) used to combine two prayers during travel.
Hadith Referenceمسند احمد / ومن مسند بني هاشم / 3288
Hadith Gradingحکم دارالسلام:صحيح، الحجاج مدلس وقد عنعن