Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) combined Zuhr and Asr, and Maghrib and Isha, in Madinah without any fear or rain. The narrator said: I asked Ibn Abbas (may Allah be pleased with them both): Why do you think he (peace and blessings be upon him) did that? He said: He (peace and blessings be upon him) wanted to make things easy for his Ummah.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10757