Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It has been expressed as a negation but its intended meaning is prohibition. So, the implication is that it is not appropriate for anyone to have any doubt about it due to its perfection and precision. An example of this usage can be found in the verse: "It was not [appropriate] for us to associate anything with Allāh" (12:38). A similar example is: "So there is [to be] no lewdness...on the Pilgrimage" (2:196). [al-Khalīl and Ibn al-Anbārī]
2. It means "There is no doubt that it is guidance for the righteous." [al-Mubarrad]
3. It means "There is no doubt that it is from Allāh." [Muqātil among other scholars]

What does it mean for there to be "no doubt" in it?

Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It means "this" (Qur'an). [Ibn ʿAbbās, Mujāhid, ʿIkrimah, al-Kisāʾī, Abū ʿUbaydah, al-Akhfash]
2. It means "that", with various opinions as to what is referred to:
(i) What was previously revealed to him of the Qur'an.
(ii) What Allāh promised to reveal to him, referring to the verse, "We will cast upon you a heavy word." (73:5).
(iii) What the people of previous scriptures were promised because they were promised a Prophet and a Book.

What does the word "that" (*dhālika*) refer to in this verse?