Sunan an-Nasa'i 3406
سنن النسائي#3406SahihIt was narrated from Ibn Tawus, from his father, that Abu As-Sahba' came to Ibn 'Abbas and said:"O Ibn 'Abbas! Did you not know that the threefold divorce during the time of the Messenger of Allah and Abu Bakr, and during the early part of 'Umar's Caliphate, used to be counted as one divorce?" He said: "Yes
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: 27:18