From your http://hibernate.org/orm/ website, I hit Source Code, then I hit download

I see, you downloaded the master branch from GitHub. This is version 5.0, not yet released and highly unstable. Unless you want to contribute to Hibernate, I suggest you download branch 4.3, or tag 4.3.6.Final. For this, either follow one of the links I provided, or click on the “branch: master” button on the page where you hit “download” and then select the branch/tag you want from the drop-down list.

If you still can’t compile, please provide us with the output of ./gradlew --version.