مَا يُجَٰدِلُ فِىٓ ءَايَٰتِ ٱللَّهِ إِلَّا ٱلَّذِينَ كَفَرُوا۟ فَلَا يَغْرُرْكَ تَقَلُّبُهُمْ فِى ٱلْبِلَٰدِ
"None dispute about the signs of God but those who deny. Do not let their moving about in the cities deceive you."
تَقَلُّبُهُمْ فِى ٱلْبِلَٰدِ — taqallub: root ق-ل-ب (to turn, to be turned about); Form V: to keep turning from one place to another. It describes going from city to city for trade, and affairs running smoothly.
What the sentence does is worth recording, and I give it as my own reading: the verse closes off an error of measure. That the other side's affairs are going well cannot be counted as proof that their position is sound. This is the logic treated at al-Aḥqāf 46/11 — "had it been good, they would not have reached it before us" — built from exactly the opposite end: there prosperity was being counted as proof; here it is said to be no proof at all.
وَجَٰدَلُوا۟ بِٱلْبَٰطِلِ لِيُدْحِضُوا۟ بِهِ ٱلْحَقَّ — "they disputed with falsehood, to make the truth slip by means of it."
إِدْحَاض — root د-ح-ض: the slipping of the foot, losing one's hold and sliding away. Makānun daḥḍun — slippery ground.
The picture in the word is worth recording: the aim is not to refute the truth — but to make it slip. That is, to shift it from its place, to turn the ground it stands on slippery. The target of the dispute is described not as showing the true to be false, but as dislodging it from where it sits.