Miraculosity of the Qur'an

Allah, the Exalted has challenged the Arabs and nonArabs to produce a qur'an similar to the Divine one. The challenge was then reduced to ten surahs, and yet they failed to do so. Finally, Allah challenged them to produce a single surah comparable to any of His.
Although they were masters of eloquence and rhetoric during that period, the Arabs were still incapable of taking up the challenge. They
realized that it could never be from anyone other than Allah, the Lord of the worlds.

The difference between miracles of the previous Messengers, which proved their veracity, and those of the Messenger of Allah, peace be on him, is that their previous miracles were effective during the lifetime of everyone of them, whereas the miracle of the Qur'an remains effective, everlasting and unchallenged until the Day of Judgment.