What must a player do before taking a penalty kick?

Before taking a penalty kick, a player must wait for the referee's whistle to proceed. This is crucial because the whistle signifies that the kick can be taken and ensures that all players are ready and positioned correctly according to the Laws of the Game. The referee's signal helps maintain order and fairness during the execution of the kick, as it prevents any premature movements from players, including those in the penalty area.

The importance of this step lies in the need to control the game and ensure that the rules are consistently applied; without the whistle, the penalty kick might be executed in a disorderly manner, leading to confusion or potential infringements. This action upholds the integrity of the game and guarantees that the opportunity for scoring is legitimately granted.