Verse 3

أَمْ يَقُولُونَ ٱفْتَرَىٰهُ بَلْ هُوَ ٱلْحَقُّ مِن رَّبِّكَ لِتُنذِرَ قَوْمًا مَّآ أَتَىٰهُم مِّن نَّذِيرٍ مِّن قَبْلِكَ لَعَلَّهُمْ يَهْتَدُونَ

They may say he has fabricated it. No such thing, this is the truth from your Lord in order to warn a people who have not received a warner before you that they may become guided.