Muwatta Malik Book 9, Hadith 5
(with regards to above) Malik said, "I believe that was during rain."
Yahya related to me from Malik from Abu'z Zubayr al-Makki from Said ibn Jubayr that Abdullah ibn Abbas said, "The Messenger of Allah, may Allah bless him and grant him peace, prayed dhuhr and asr together and maghrib and isha together, and not out of fear nor because of travelling."
Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to join the prayer along with the amirs if they joined maghrib and isha in the rain.