Surah Qaf — Ayah 2 (50:2)
بَلۡ عَجِبُوٓاْ أَن جَآءَهُم مُّنذِرٞ مِّنۡهُمۡ فَقَالَ ٱلۡكَٰفِرُونَ هَٰذَا شَيۡءٌ عَجِيبٌ ٢
English translation (Saheeh International)
But they wonder that there has come to them a warner from among themselves, and the disbelievers say, "This is an amazing thing.
Brief commentary
The cause of their rejection was not that they expected you to lie, because they know your honesty. Rather, they are amazed that a warning messenger came to them from their own species, not from the angels. They say, in amazement, “A human messenger coming to us is a strange thing!”