(فَلَمَّا جَاءَ السَّحَرَةُ قَالُوا لِفِرْعَوْنَ أَئِنَّ لَنَا لَأَجْرًا)

Meaning: Shall there be for us a great reward?

(إِنْ كُنَّا نَحْنُ الْغَالِبِينَ)

For Moses, peace be upon him. Perhaps they stated the condition in this manner to mirror the style of those who speak in such a way, as a form of agreement with them. Otherwise, it would not be fitting for their state to express doubt regarding their own victory.