Here Allah speaks of the lies and fabrications of the idolaters, when they devoted some of their cattle to their false gods and some to Allah, as He described in Surat Al-An'am where He said:

{And they assign to Allah share of the tilth and cattle which He has created, and they say: "This is for Allah" according to their claim, "and this is for our partners." But the share of their partners reaches not Allah, while the share of Allah reaches their partners! Evil is the way they judge!} (6:136).
Similarly, out of the two kinds of offspring, sons and daughters, they assigned to Him the worst and least valuable (in their eyes), i.e., daughters, as Allah says:

{Is it for you the males and for Him the females? That indeed is a division most unfair !} (53:21-22)

And Allah says here:

{they assign to some of His servants a share with Him. Verily, man is indeed a manifest ingrate !} Then He says:

This is a denunciation of them in the strongest terms, as He goes on to say:

means, if one of these people is given the news that there has been born to him one of those which he attributes to Allah, i.e., a daughter, he hates this news and it depresses and overwhelms him so much that he keeps away from people because he feels so ashamed. Allah says, so how can they dislike that so much and yet they attribute it to Allah?

means, women are regarded as lacking something, which they make up for with jewelry and adornments from the time of childhood onwards, and when there is a dispute, they cannot speak up and defend themselves clearly, so how can this be attributed to Allah?

means, that is what they believe about them, but Allah denounces them for that and says:

{Did they witness their creation ?} meaning, did they see Allah creating them as females?

{Their testimony will be recorded,} means, concerning that,

{and they will be questioned !} means, about that, on the Day of Resurrection. This is a stem warning and a serious threat.

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:

{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)

{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:

{They have no knowledge whatsoever of that.} meaning, of the truth of what they say and the arguments they put forward.

{They do nothing but lie!} means, they tell lies and fabricate untruths.

Mujahid said, "They do not appreciate the power of Allah."