How authentic is the Hadith that calls for safeguarding oneself from a scholar's slip and a hypocrite's debate using the Qur’an, and clarifies how to recognize a scholar's slip as being the reprehensible statement that one finds astonishing?

A hadith with this exact wording has not been narrated. However, warnings against the slip of a scholar and the disputation of a hypocrite using the Qur'an have been reported with other wordings. Among them is what Al-Darimi narrated from Umar ibn Al-Khattab, that what destroys Islam is "the slip of a scholar, the disputation of a hypocrite using the Book, and the rule of misleading leaders."

Abu Dawud narrated from Mu'adh ibn Jabal that he warned against tribulations in which wealth would abound and the Qur'an would be widely available. Some people might claim to follow the Qur'an while in reality following their whims. He also warned against the deviation of a wise person, as Satan might utter a word of misguidance through his tongue, and a hypocrite might utter a word of truth.

When Mu'adh was asked how to recognize the slip of a scholar, he replied that it is what seems ambiguous to the listener from the scholar's statement, or what the hearts of believers denounce and do not recognize.