It was narrated that Ibn 'Abbas said:
"The Messenger of Allah (ﷺ) prayed Zuhr and 'Asr together, and Maghrib and 'Isha' together, when there was no fear and he was not traveling." (JA)
English reference (JA): Vol. 1, Book 6, Hadith 602 (JA)
Arabic reference (JA): Book 6, Hadith 608 (JA)