Historical Rules · 1 October 2012
Rule 603.6e
Official source text from the 1 October 2012 Rules release
Some permanents have text that reads "[This permanent] enters the battlefield with . . . ," "As [this permanent] enters the battlefield . . . ," "[This permanent] enters the battlefield as . . . ," or "[This permanent] enters the battlefield tapped." Such text is a static ability -- not a triggered ability -- whose effect occurs as part of the event that puts the permanent onto the battlefield.