وَقَالُوا لَوْ شَاء الرَّحْمَنُ مَا عَبَدْنَاهُم
And they said;"If it had been the will of the Most Gracious, we should not have worshipped them."
means, (they said;) `if Allah had willed, He would have prevented us from worshipping these idols which are images of the angels who are the daughters of Allah; He knows about this and He approves of it.'
By saying this, they combined several types of error;
First;They attributed offspring to Allah -- exalted and sanctified be He far above that.
Second;They claimed that He chose daughters rather than sons, and they made the angels, who are the servants of the Most Gracious, female.
Third;They worshipped them with no proof, evidence or permission from Allah. This was based on mere opinion, whims and desires, imitation of their elders and forefathers, and pure ignorance. They used Allah's decree as an excuse, and this reasoning betrayed their ignorance.
Fourth;Allah denounced them for this in the strongest terms, for from the time He first sent Messengers and revealed Books, the command was to worship Him Alone with no partner or associate, and it was forbidden to worship anything other than Him.
Allah says;
وَلَقَدْ بَعَثْنَا فِى كُلِّ أُمَّةٍ رَّسُولاً أَنِ اعْبُدُواْ اللَّهَ وَاجْتَنِبُواْ الْطَّـغُوتَ فَمِنْهُم مَّنْ هَدَى اللَّهُ وَمِنْهُمْ مَّنْ حَقَّتْ عَلَيْهِ الضَّلَـلَةُ فَسِيرُواْ فِى الاٌّرْضِ فَانظُرُواْ كَيْفَ كَانَ عَـقِبَةُ الْمُكَذِّبِينَ
And verily, We have sent among every Ummah a Messenger (proclaiming);"Worship Allah, and avoid all false deities."
Then of them were some whom Allah guided and of them were some upon whom the straying was justified.
So travel through the land and see what was the end of those who denied. (16;36)
وَاسْيلْ مَنْ أَرْسَلْنَا مِن قَبْلِكَ مِن رُّسُلِنَأ أَجَعَلْنَا مِن دُونِ الرَّحْمَـنِ ءَالِهَةً يُعْبَدُونَ
And ask those of Our Messengers whom We sent before you;"Did We ever appoint gods to be worshipped besides the Most Gracious" (43;45)
And Allah says in this Ayah, after mentioning this argument of theirs;
مَّا لَهُم بِذَلِكَ مِنْ عِلْمٍ
They have no knowledge whatsoever of that.
meaning, of the truth of what they say and the arguments they put forward.
إِنْ هُمْ إِلاَّ يَخْرُصُونَ
They do nothing but lie!
means, they tell lies and fabricate untruths.
Mujahid said about
مَّا لَهُم بِذَلِكَ مِنْ عِلْمٍ إِنْ هُمْ إِلاَّا يَخْرُصُونَ
(They have no knowledge whatsoever of that. They do nothing but lie!),
"They do not appreciate the power of Allah.