Sura al-Aḥqāf 46:8

أَمْ يَقُولُونَ ٱفْتَرَىٰهُ قُلْ إِنِ ٱفْتَرَيْتُهُۥ فَلَا تَمْلِكُونَ لِى مِنَ ٱللَّـهِ شَيْـًٔا هُوَ أَعْلَمُ بِمَا تُفِيضُونَ فِيهِ كَفَىٰ بِهِۦ شَهِيدًۢا بَيْنِى وَبَيْنَكُمْ وَهُوَ ٱلْغَفُورُ ٱلرَّحِيمُ

am yaqūlūna iftarāhu qul ini iftaraytuhu fa-lā tamlikūna lī mina allāhi shayʾan huwa aʿlamu bi-mā tufīḍūna fīhi kafā bihi shahīdan baynī wa-baynakum wa-huwa l-ghafūru l-raḥīmu

Or do they say, "He has forged it"? Say: "Had I forged it, then can ye obtain no single (blessing) for me from Allah. He knows best of that whereof ye talk (so glibly)! Enough is He for a witness between me and you! And he is Oft-Forgiving, Most Merciful."