Fir`awn describes Musa's Proofs as being Magic and Their Agreement to hold a Contest

Allah, the Exalted, informs of what Fir`awn said to Musa when he showed him the great proof. This great sign to Fir`awn was Musa casting down his stick which became a huge snake, and his pulling his hand out from under his arm while it was glowing white without any illness. At this, Fir`awn said, "This is magic that you have brought to us to bewitch us and conquer the people, so that they will follow you. Then you will outnumber us." Fir`awn then said, "Your plan will not work. We have magic just like yours, so do not let yourself be deceived by that what you are doing."

فَاجْعَلْ بَيْنَنَا وَبَيْنَكَ مَوْعِداً

مَوْعِدُكُمْ يَوْمُ الزِّينَةِ وَأَن يُحْشَرَ‌ النَّاسُ ضُحًى (Your appointment is the festival day and that the people are assembled at forenoon - 20:59). يَوْمُ الزِّينَةِ has been explained differently by different authorities. Some say it was a special festival when the Egyptians, attired in beautiful dresses, gathered outside the towns, while others say that it was a Saturday (' یوم السَّبت), and according to some others it was the tenth day of Muharram (عاشُورا).

The great advantage in fixing for the contest