Envy was a brick wall and was a tower. There was no way some poor, pitiful human was going to even try and strike at him without repercussions. It was a game of cat and mouse.
Envy grabbed the man's arm as he started to advance towards Sloth. It wasn't out of jealousy, or maybe it was. He clicked his tongue, wagging his pocket knife back and forth with the blade exposed. It was a fair warning, though he could easily widdle his fingers right off the hand.
He let go of his arm, shoving him forward with the tip of the knife jabbing at the small of the man's back. He was giving Sloth the opportunity to nibble. To see if she could be impressive. He was taunting her as much as he was the buyer.