swear in
 [phrasal verb]
swear in及物短语动词。
swear (someone) in or swear in (someone)
: to place (someone) in a new office or position by having an official ceremony in which that person makes a formal promise to do the work properly, to be honest and loyal, etc.

When do they swear him in? 主动语态

— often used as (be) sworn in 被动语态
The new president will be sworn in tomorrow.