﴿ بَلْ أَتَيْنَٰهُم بِٱلْحَقِّ وَإِنَّهُمْ لَكَٰذِبُونَ ﴾

“Nay, We have conveyed unto them the truth: and yet, behold, they are intent on lying [to them­selves]!”

(Nay, but We have brought them the Truth) We sent Gabriel to their Prophet with the Qur'an in which it is stated that Allah has no son or partner, (and lo! they are liars) when they say the angels are Allah's daughters.