ʿAbd Allāh ibn ʿAbbās—who transmitted it from the Prophet, may Allah bless him and grant him peace—said:

“The Messenger of Allah, peace and blessings be upon him, used to teach us the tashahhud just as he would teach us a sūrah from the Qur’an. He would say:
‘All greetings, all blessed greetings, all prayers, all pure words belong to Allah. Peace be upon you, O Prophet, and the mercy of Allah and His blessings. Peace be upon us and upon the righteous servants of Allah. I bear witness that there is no god but Allah, and that Muhammad is the Messenger of Allah.’”

Reason for the divergence:
Their difference stems from the varying degrees of probability they assigned to the relative strength of these three reports. Whoever deemed one report stronger inclined toward it. Many jurists held that the matter is one of choice—like the call to prayer (adhān), the takbīr over the deceased, the takbīr in the two ʿĪds, and other rites whose transmission is mass-reported—and this is the correct view, and Allah knows best.

Al-Shāfiʿī stipulated that sending blessings upon the Prophet—peace and blessings be upon him—must be included in the tashahhud. He declared it obligatory on the basis of the Almighty’s words:
“O you who believe, invoke blessings upon him and greet him with salutations of peace.” (al-Aḥzāb 33:56)
He understood the “salutation” in the verse to mean the taslīm that concludes the prayer. The majority, however, held that it refers to the salutation pronounced after one has already invoked blessings upon him. Some literalist scholars (ahl al-ẓāhir) considered it compulsory for the worshiper, during the tashahhud, to seek refuge from the four matters mentioned in the ḥadīth: the punishment of the grave, the punishment of Hell, the trial of the False Messiah, and the trials of life and death. This is because it is authentically reported that “the Messenger of Allah, peace and blessings be upon him, used to seek refuge from them at the end of his tashahhud,” and in one wording: “When any of you finishes the final tashahhud, let him seek refuge from four.” Muslim narrated the ḥadīth.

Eighth Issue: They disagreed about the taslīm that ends the prayer. The majority held it to be obligatory, whereas Abū Ḥanīfah said it is not obligatory. Among those who deem it obligatory, some say that a lone worshiper and an imam are required to offer one taslīm, while others insist on two. The majority follow the apparent purport of ʿAlī’s ḥadīth in which he—peace and blessings be upon him—said, “Its exit is the taslīm.” Those who oblige two taslīms rely on the established report that “he—peace and blessings be upon him—used to give two taslīms,” considering his practice indicative of obligation.