So the magicians fell down in prostration. They said, "We have believed (20:70)

Almuntakhab Fi Tafsir Alquran Alkarim

There and then fell the necromancers prostrate in adoration and they prostrated their reason to divine revelation and said: We do recognize Allah, the Creator, of Mussa and Harun

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(20:70) Accordingly, at the end of the encounter, all the magicians were cast down to prostration *43 and they cried out, "We believe in the Lord of Aaron and Moses. " *44

So the magicians fell down in prostration. They said, "We have believed meaning

*43) When they saw the power of the staff of Moses, they involuntarily fell prostrate as if some one had trade them do so, because they were convinced that it was a miracle and not a feat of tragic.
*44) This profession of faith by the magicians shows that every one was aware of the basic object of the encounter. It was not an encounter between the feats of the magicians and those of Prophet Moses, but it was to decide whether the claim of Prophet Moses that he was a Messenger of Allah was true or not. If this staff was actually turned into a dragon, it was by means of a miracle. On the other hand, Pharaoh intended to prove by the feats of his magicians that it was not a miracle but a feat of magic. Incidentally, this also shows that Pharaoh and his magicians and the common people fully understood the distinction between a miracle and a feat of magic. ,That is why when the magicians saw that it was a miracle shown by the power of Allah which had exposed their magic, they did not say that Moses was a more skilful magician, but straightway fell prostrate, saying, "We believe in the Lord of Aaron and Moses."
It is obvious that the defeat turned the tables on Pharaoh who had himself arranged the encounter "to expose" Prophet Moses. He had mustered all his magicians with a view to demonstrating before the public that there was nothing extraordinary in turning a staff into a serpent for this could be done by every magician. But the defeat of the magicians and their acknowledgment testified that Moses was real]y a Messenger of Allah and the transformation of the staff was not a feat of magic but a miracle.
 

So the magicians fell down in prostration. They said, "We have believed meaning in Urdu

آخر کو یہی ہُوا کہ سارے جادوگر سجدے میں گرا دیے گئے اور پکار اٹھے "مان لیا ہم نے ہارونؑ اور موسیٰؑ کے رب کو"