Sunan an-Nasa'i 601
سنن النسائي#601Sahihأَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنْ أَبِي الزُّبَيْرِ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ صَلَّى رَسُولُ اللَّهِ صلى الله عليه وسلم الظُّهْرَ وَالْعَصْرَ جَمِيعًا وَالْمَغْرِبَ وَالْعِشَاءَ جَمِيعًا مِنْ غَيْرِ خَوْفٍ وَلاَ سَفَرٍ .
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
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 6:108