Simples Assim

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    ...
    <session-factory name="java:hibernate/SessionFactory">
        ...
        <property name="show_sql">false</property>
        ...
    </session-factory>
    ...
</hibernate-configuration>

http://docs.jboss.org/hibernate/core/3.3/reference/en/html/session-configuration.html