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

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]