The ball hits your hand on the racket
Under the FIP wording, a shot from the other pair that hits any part of you or your kit other than the racket loses you the point. The hand holding the racket is part of you, not the racket.
The rule
You lose the point if a ball hit by the other pair touches any part of your body or equipment apart from the racket before you have played it. The rules make no exception for the hand or fingers holding the grip.
In practice
A ball that glances off your knuckles and flies over the net is not a good shot under that wording. It is often very hard to see, so it is usually the player whose hand was hit who knows. Say so straight away.
Your own shot
The same idea works the other way: after you hit the ball, it must not touch you, your partner or anything you are wearing. A mishit that clips your own wrist loses the point too.
Preguntas
Is the hand part of the racket in padel?
No. The FIP rules only exempt the racket, so a ball off your hand loses the point.