Shirtless Justin Bieber Raps Big Sean's 'IDFWU' in Las Vegas

Ari Perilstein/Getty Images for Variety
Justin Bieber attends the 2014 Young Hollywood Awards brought to you by Samsung Galaxy at The Wiltern on July 27, 2014 in Los Angeles, California.  

There are specious rumors that Justin Bieber may have had something to do with Ariana Grande and Big Sean's split, but the Biebs still remains a fan. 

Prior to the big fight over the weekend between Floyd Mayweather and Manny Pacquiao (which Bieber attended), Bieber was caught on video at an outdoor Vegas club shirtless (and nearly pantless) lip-syncing to Big Sean's No. 1 Top Hip-Hop/R&B hit "I Don't Fuck With You." Points for solid commitment throughout, though we guess his upcoming Lip Sync Battle performance will be a little less PG-13. 

Check out the impromptu performance below, courtesy of TMZ