Which command is used to validate the syntax of a configuration without applying the configuration?

The `commit check` command is specifically designed to perform a syntax and semantic validation of the candidate configuration without activating it. This allows administrators to verify the configuration's correctness before making it operational, preventing potential service disruptions.

The `commit confirmed` command applies the configuration, but automatically rolls it back after a specified timeout if not confirmed, which is not merely checking syntax.

The `commit synchronize` command applies and synchronizes the configuration across multiple Routing Engines, thus activating the changes.

The `commit and-quit` command applies the configuration and then exits configuration mode, making the changes active.