James Harrison says Pittsburgh Steelers head coach Mike Tomlin "handed me an envelope" after one of the most vicious hits of his career ... calling it the "G-est thing" Tomlin ever did.
The hit Harrison is referring to went down against the Cleveland Browns in 2010 ... when he led with his helmet and laid out a defenseless Mohamed Massaquoi.
The hit resulted in a $75,000 fine and Massaquoi left the game with a concussion ... and now, Harrison is sharing his side of the infamous incident.
"Listen, on everything I love, on my daddy’s grave, I hit that man with about 50% of what I had and I just hit him because I wanted him to let loose of the ball," Harrison told Barstool Sports' "Going Deep" podcast.