Justin Bieber: What Do You Mean 'Purose?'

Justin Bieber's world tour opener at KeyArena went off without a hitch, with one small exception -- the people who made some of his merch would've bombed in a 3rd grade spelling bee.

One of the t-shirts sold inside the concert had white lettering that read, "Many Are The Plans In A Person's Heart, But It Is God's Purose that Prevails." Ooops.

We found out Bitter Face Vending Inc. was hawking the gear ... but it was printed by a company called Bravado. One "Belieber" told us she dropped $45 for one, but didn't notice the error because of all the mayhem surrounding the booth.

She said she's looking to get refunded and she's in luck.

Bieber's people tell TMZ ... they're aware of the mistake and they've recalled all the bad tees, and anyone who bought one can exchange it for a corrected shrt.