Sunan an-Nasa'i 603
سنن النسائي#603SahihIt was narrated that Ibn 'Abbas said:"I prayed behind the Messenger of Allah (ﷺ) eight (Rak'ahs) together and seven (Rak'ahs) together
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
In-book reference: 6:110