These are the verses about sihr in Soorat al-A’raaf, where Allaah says (interpretation of the meaning):

“And We revealed to Moosa (saying): ‘Throw your stick,’ and behold! It swallowed up straight away all the falsehood which they showed.

Thus truth was confirmed, and all that they did was made of no effect.

So they were defeated there and returned disgraced

[al-A’raaf 7:117-119]