"Has he made the gods"—as an interrogation from them—"into one God?" That is, he has done so when he called them to the worship of Allah alone. "Indeed, this is a curious thing." Curious ('ujab) and amazing ('ajib) are synonymous, like 'tiwal' and 'tawil' (long), 'arad' and 'arid' (wide), and 'kibar' and 'kabir' (great).
﴿أجعَل الْآلهَة﴾ عَلَى الِاسْتِفْهَام مِنْهُم ﴿إِلَهًا وَاحِدًا﴾ أَي: قد فعل حِين دعاهم إِلَى عبَادَة اللَّه وَحده ﴿إِنَّ هَذَا لَشَيْءٌ عُجَابٌ﴾ عجب [عُجاب وَعَجِيب وَاحِد , مثل طوال وطويل , وعراض وعريض , وكبار وكبير].