قَالَ بَلْ أَلْقُوا
...
"...or we be the first to throw!"
(Musa) said: "Nay, throw you (first)!"
This means, `you magicians should go first so that we can see what magic you are going to perform and so that the true state of their affair will become obvious to the people.'
...
فَإِذَا حِبَالُهُمْ وَعِصِيُّهُمْ يُخَيَّلُ إِلَيْهِ مِن سِحْرِهِمْ أَنَّهَا تَسْعَى
Then behold! their ropes and their sticks, by their magic, appeared to him as though they moved fast.
In another Ayah it says that when they threw,
وَقَالُواْ بِعِزَّةِ فِرْعَونَ إِنَّا لَنَحْنُ الْغَـلِبُونَ
Then said: "By the might of Fir`awn, it is we who will certainly win!" (26:44)
And Allah, the Exalted, says,
سَحَرُواْ أَعْيُنَ النَّاسِ وَاسْتَرْهَبُوهُمْ وَجَأءُو بِسِحْرٍ عَظِيمٍ
They bewitched the eyes of the people, and struck terror into them, and they displayed a great magic. (7:116)
Here, He says in this Surah,
...
فَإِذَا حِبَالُهُمْ وَعِصِيُّهُمْ يُخَيَّلُ إِلَيْهِ مِن سِحْرِهِمْ أَنَّهَا تَسْعَى
Then behold! their ropes and their sticks, by their magic, appeared to him as though they moved fast.
They were a large numbered group and each one of them threw a stick and a rope until the valley became full of snakes piled on top of each other.
Concerning Allah's statement,
فَأَوْجَسَ فِي نَفْسِهِ خِيفَةً مُّوسَى