To run additional goals after release preparation but before committing, specify them using the preparationGoals property.
<project>
[...]
<build>
[...]
<plugins>
[...]
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-release-plugin</artifactId>
<version>2.4.2</version>
<configuration>
<preparationGoals>clean verify</preparationGoals>
</configuration>
</plugin>
[...]
</plugins>
[...]
</build>
[...]
</project>