It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) combined the Zuhr and Asr prayers together (i.e., he joined them), and the Maghrib and Isha prayers together (i.e., he joined them), without fear and without travel.
Imam Malik (may Allah have mercy on him) said: In my opinion, perhaps this incident occurred at the time of rain.