The Quran

أَمِ اتَّخَذوا مِن دونِهِ آلِهَةً ۖ قُل هاتوا بُرهانَكُم ۖ هٰذا ذِكرُ مَن مَعِيَ وَذِكرُ مَن قَبلي ۗ بَل أَكثَرُهُم لا يَعلَمونَ الحَقَّ ۖ فَهُم مُعرِضونَ

Muhammad Asad

and yet,¹ they choose to worship [imaginary] deities instead of Him! Say [O Prophet]: "Produce an evidence for what you are claiming:² this is a reminder [unceasingly voiced] by those who are with me, just as it was a reminder [voiced] by those who came before me."³But nay, most of them do not know the truth, and so they stubbornly turn away [from it]⁴ -

See note 24 above.
Lit., "produce your evidence", i.e., for the existence of deities other than God, as well as for the intellectual and moral justification of worshipping anything but Him.
I.e., the earlier prophets, the purport of whose messages was always the stress on the oneness of God.
In other words, most people's obstinate refusal to consider a reasonable proposition on its merits is often due to no more than the simple fact that it is not familiar to them.