The magic trick with the hands, drawing and hiding the disk, is a display of supreme confidence in the hero’s own abilities. Which is just about all that he has left.
In the legendary voyeuristic opening sequence, the whole further drama is spelt out with the shot of the hands injecting the medicine. By resurrecting the woman, the agent is playing God and will have to pay for it dearly.
When contacting HQ, he has blood on his hands. This is undeniable and visible guilt. Soon he is the only suspect and there’s nothing he can say to deny the blood. He clenches his fist in the decisive moment in the aquarium, when balance is broken and all his energy and skill will be dedicated to redemption. Later, the blood is washed and the game of restoring the balance is on.
In yet another tense “rope” tracking shot, De Palma shows how the fate of the character is held by the hands of the team, infusing wild paranoia and multiplying the suspense.
The dangerous drop of sweat in the heist scene is another symbol of how he can’t escape his humanity, even though he has excelled to be a ghost. But being flesh and blood ultimately helps – his hand gets him out of the impossible situation.
In the ultimate action sequence, Ethan arms his hand with the explosive and pushes aside the psychological torment from his conflict with the Father figure. Then he flies away completely on his own, reborn.