This rather dramatic gesture is meant to indicate that because the two families will soon be one, this is the last time the sword will ever be raised by the groom or his family in the bride's house. Since in pre-colonial Rajasthan, Rajput marriages often took place between warring clans in order to form political alliances, this act was a very important one.
There is some ambiguity in message of the sword as it also serves as a warning to the brides family that if they were thinking about starting any trouble at this point (I don't know maybe the scenario of the whole wedding as an elaborate set-up for an ambush) the groom's family is ready and prepared to fight.