The Qur’an states that it is a perfect book preserved on tablets in heaven (Surah 85:21-22).
If the Qur’an is a perfect book from Allah, then there shouldn’t be any contradictions in it.
Of course, the Muslims will deny that any contradictions exist in the Qur’an, but they do.
Some of the contradictions below could be debated, but some of them are clearly contradictions.
A contradiction occurs when one statement on a subject excludes the possibility of another. The first one here is a good example. In Surah 19:67, it states that man was created out of nothing. In 15:26, man is created from clay. Since clay is something, we have a contradiction since “nothing” excludes the possibility of “clay.” Both cannot be true.
All quotes from the Qur’an, unless otherwise specified, are from Yusuf Ali and can be found at the Qur’an online.