Question

How do I get Jirachi in Sapphire?

Answer 1

I am sorry but you just can't get Jirachi in Pokemon Sapphire, there was an event a LONG
time ago.

This is the only way you can get it-

Obtain from Special Event, Colosseum Bonus Disk or Pokémon Channel-Serebii.net

For more info go here- http://www.serebii.net/pokedex-rs/385.shtml or go here http://serebii.net/events/dex/385.shtml (look in the 2006 section)

Hope this helps you =P

Answer 2

You can't get Jirachi in Saffire, it was an event.
>Obtain from Special Event, Colosseum Bonus Disk or Pokémon Channel -Serebii

Here are all the Jirachi events.