It is narrated from Ibn Abbas (may Allah be pleased with them both) that he stated: The Messenger of Allah (peace be upon him) combined the Zuhr and Asr prayers, and the Maghrib and Isha prayers, without fear or travel. Imam Malik (may Allah have mercy on him) said: In my opinion, this was during rain.
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 366
Hadith Takhrijأخرجه مسلم: صلاة المسافرين، باب الجمع بين الصلاتين في الحضر (705) - ومالك في الموطأ: الصلاة، باب الجمع بين الصلاتين في الحضر والسفر.