Surah Al-Furqan, ayah 4

25:4

وَقَالَ ٱلَّذِينَ كَفَرُوٓاْ إِنۡ هَٰذَآ إِلَّآ إِفۡكٌ ٱفۡتَرَىٰهُ وَأَعَانَهُۥ عَلَيۡهِ قَوۡمٌ ءَاخَرُونَۖ فَقَدۡ جَآءُو ظُلۡمٗا وَزُورٗا ٤

Waqālal-ladhīna kafarū in hādhā illā ifkuniftarāhu wa a'ānahū 'alayhi qawmun ākharūna faqad jā'ū zulman wazūrā

And those who disbelieve say, "This [Qur’ān] is not except a falsehood he invented, and another people assisted him in it." But they have committed an injustice and a lie.