Sunan Abu Dawud
2200
Sahih+2

Tawus said:Abu al-Sahba' said to Ibn Abbas: Do you know that a divorce by three pronouncements was made a single one during the time of the Prophet (ﷺ), and of AbuBakr and in the early days of the caliphate of Umar? He replied: Yes

SahihAl-Albani
SahihMuhammad Muhyi Al-Din Abdul Hamid