Sunan an-Nasa'i 601
سنن النسائي#601SahihIt 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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 6:108