Bill Russell gives Charles Barkley the bird at the NBA Awards show.

While hall of famers Charles Barkley and Kareem Abdul-Jabbar were setting up to give the Lifetime Achievement Award to Oscar Robertson at the NBA Awards show, Barkley was taking a moment to thank some of the greats that came before him, Elgin Baylor and Bill Russell.

After thanking Baylor, Barkley then gave his thanks to Russell, but the Celtics legend replied with the most memorable, entertaining moment of the night:

(Warning: middle fingers incoming)

Sorry everyone, I forgot it was live TV & I can’t help myself whenever I see Charles it just is pure instinct. @NBAonTNT @NBA #birdman #NBAAwards pic.twitter.com/0zQLvWhuKi

— TheBillRussell (@RealBillRussell) June 26, 2018

The 11-time champion apologized through his Twitter account and left a funny note at the end.

Video: NBAgamingboy