A number of reasons are supplied for this washing:

a) During the course of the night, our souls ascend to the heavenly realms, where they "recharge"; drawing renewed life and energy for the following day. At that time, our bodies remain with only the lowest soul-powers—those that control our mechanical functions, such as the digestive and respiratory systems. The spiritual vacuum that ensues allows forces of impurity to cleave to the body. When we awaken in the morning we ritually wash our hands to remove the last remaining vestiges of these foreign influences.

b) G‑d returns our souls to our bodies every morning. The reason? There is a specific mission we have to accomplish today. We were given another day to serve G‑d. In this way, we are similar to the priest who is about to serve in the Holy Temple. Just as the priests were required to wash their hands before service, so, too, we wash our hands before beginning our day's service.

c) During the night, chances are that our hands have touched areas of our bodies which are normally covered. After touching such areas we are required to wash our hands before reciting the morning blessings and prayers.

Click here for more about the morning hand washing, including the prescribed procedure for this ritual.

Yours truly,

Rabbi Menachem Posner