To what extent is it true that the wording of the Shahada, "There is no god but Allah, Muhammad is the Messenger of Allah," appears word-for-word in the Hadith, and what is the way to confirm or deny its authenticity, especially given that it does not appear in this wording in the Six Books, and Shaykh Al-Albani did not authenticate it?

The Hadith "I have been commanded to fight the people until they say there is no god but Allah" appears in multiple sources. Al-Tabari and Al-Bayhaqi reported it with an interpretive addition to the Qur'anic verses, stating that the word of monotheism is "there is no god but Allah, Muhammad is the Messenger of Allah." Ibn Kathir explicitly stated that this addition is an interpolation from the words of Al-Zuhri.

As for the authentic narration in Al-Bukhari and Muslim, it is limited to "there is no god but Allah."

Despite this, the addition "Muhammad is the Messenger of Allah" is not problematic, as it was reported in another Hadith in the Two Sahihs from Ibn Umar with the wording, "until they bear witness that there is no god but Allah and that Muhammad is the Messenger of Allah."

Accordingly, the Hadith is authentically established from the Prophet, peace be upon him, and the ultimate purpose of fighting is the monotheism of Allah by uttering the two testimonies of faith.