The tradition mentioned above has also been transmitted by Sahl bin Sa’d Al Sa’idi through a different chain of narrators. This version has “He divorced her three times before the Messenger of Allah (ﷺ). The Messenger of Allah (ﷺ) implemented it and what is done before the Prophet (ﷺ) is sunnah(model behavior of the Prophet). Sahl said “I attended this before the Messenger of Allah(ﷺ). Afterwards the sunnah about those who invoked curses on each other was established that they (the spouses) were separated from each other and they would never be united.”

English translation · Sunan Abu Dawud