Al-A'raf - 7:106

قَالَ إِن كُنتَ جِئْتَ بِآيَةٍ فَأْتِ بِهَا إِن كُنتَ مِنَ الصَّادِقِينَ
[7:106]
He said: If you have come with a sign, then bring it, if you are of the truthful ones.
(Pharaoh) said: "If indeed thou hast come with a Sign, show it forth,- if thou tellest the truth."
(Pharaoh) said: If thou comest with a token, then produce it, if thou art of those who speak the truth.