Surah 20. Ta-Ha, Ayah 62

They knew that they had here to deal with no ordinary man, but a man with powers above what they could conceive of. But evil always thinks evil. Judging Moses and Aaron by their own standards, they thought that these two were also tricksters, with some tricks superior to their own. All they had to do was to stand together, and they must win. I construe xx. 63-64 to be private talk among themselves, followed by their open challenge to Moses in xx. 65.