What was the form and wording of divorce during the time of the Messenger of Allah, peace and blessings be upon him, and what change occurred to it during the time of Umar ibn al-Khattab, may Allah be pleased with him?

If the question is about the Hadith of Ibn Abbas which indicates that a triple divorce was considered a single divorce during the time of the Prophet (peace be upon him), Abu Bakr, and for two years of Umar’s caliphate, and that Umar then enforced it as three, then the answer is that this Hadith is authentic. The scholars have addressed the issue of Umar’s deviation from what was in the early days of Islam with several answers. The soundest of these is what Al-San'ani mentioned: that the Hadith pertained to a specific situation, which was the repetition of the divorce wording (e.g., "You are divorced, you are divorced"). During the time of the Prophet and afterward, people were presumed to be sincere and truthful, so the claim of someone who asserted that the second utterance was a confirmation of the first, rather than the establishment of another divorce, was accepted. When Umar observed a change in people's circumstances and the prevalence of false claims, he deemed it expedient to hold the speaker accountable for the apparent meaning of his words and not to believe his claim about his inner intention. This answer was approved by Al-Qurtubi, and Al-Nawawi said: "It is the soundest of the answers." Some scholars interpreted the Hadith to mean that people during the time of the Prophet (peace be upon him) would pronounce a single divorce instead of three, and they did not utter a triple divorce until Umar's time, so he enforced it as three.