The mu‘jizah (miracle) is the extraordinary sign with which Allah supports His Prophets and Messengers, and challenges people.
أَفَلَا يَتَدَبَّرُونَ الْقُرْآنَ ۚ وَلَوْ كَانَ مِنْ عِندِ غَيْرِ اللَّهِ لَوَجَدُوا فِيهِ اخْتِلَافًا كَثِيرًا
Then do they not reflect upon the Qur’an? If it had been from [any] other than Allah, they would have found within it much contradiction. (Al-Qur’an 4:82)