Too simple. Let's twist this around: A1 has used his dribble. B1 reaches out to make a steal, and simply touches the ball, without A1 losing possession. A1 begins a new dribble. Legal play?
Bonus question: A1 has used his dribble. A2 running near A1, reaches out, and simply touches the ball, without A1 losing possession. A1 begins a new dribble. Legal play?