Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(And they) the disbelievers of Mecca (worship instead of Allah that for which no warrant has been revealed unto them) without any Scripture or pretext, (and that whereof they have no knowledge) proof or clarification. (For evil-doers) for idolaters (there is no helper) to save them from Allah's chastisement.
And they, the idolaters, worship besides God that, namely, idols, for which He has never revealed any warrant, [any] definitive proof, and that of which they have no knowledge, [when they claim] that these are gods. And those who do evil, by way of [practising] idolatry, shall have no helper, to protect them against God’s chastisement.
The Idolators' worship of others besides Allah and Their vehement rejection of the Ayat of Allah
Allah tells us that the idolators, in their ignorance and disbelief, worship besides Allah others which He has sent down no authority for, i.e., no proof or evidence for such behavior. This is like the Ayah:
(for which He has sent down no authority, and of which they have no knowledge;) meaning, they have no knowledge in the subject that they fabricate lies about; it is only something which was handed down to them from their fathers and ancestors, with no evidence or proof, and its origins lie in that which the Shaytan beautified for them and made attractive to them. Allah warned them:
وَمَا لِلظَّـلِمِينَ مِن نَّصِيرٍ
(and for the wrongdoers there is no helper.) meaning, no one to help them against Allah when He sends His punishment and torment upon them. Then Allah says:
وَإِذَا تُتْلَى عَلَيْهِمْ ءَايَـتُنَا بَيِّنَاتٍ
(And when Our clear Ayat are recited to them, ) means, when the Ayat of the Qur'an and clear evidence and proof for Tawhid of Allah are mentioned to them, and they are told that there is no god besides Allah and that the Messengers spoke the truth,
(They are nearly ready to attack with violence those who recite Our Ayat to them.) then they nearly attack and do harm to those who bring proof to them from the Qur'an, and cause them harm using their tongues and hands.
(Shall I tell you of something worse than that The Fire which Allah has promised to those who disbelieved,) The fire and wrath and torment of Allah are far worse than that with which you are trying to scare the believing close friends of Allah in this world. The punishment in the Hereafter for these deeds of yours is worse than that what you claim you want to do to the believers.
(and worst indeed is that destination!) how terrible is the Fire as a final destination and abode!
إِنَّهَا سَآءَتْ مُسْتَقَرّاً وَمُقَاماً
(Evil indeed it is as an abode and as a place to rest in. ) 25:66
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
That is, "Neither there is any mention of their deities in any revealed Book nor have they any other source of knowledge about them nor any authority to worship them. Therefore, it is sheer ignorance that they have associated their self invented deities with Allah and worship them, make vows and offer sacrifices to them and supplicate them for their needs etc.
This is to warn the foolish people that they are absolutely wrong in expecting that their deities would help them in this world and in the Hereafter? because they have no power to help them. Thus, they will find no helper, for Allah alone could help them and they have already displeased Him by their rebellious behavior.
That is, "You will meet with a far worse state of anguish than that which you display against those who recite Divine Revelations to you.