The hand, in one form or another, has been a common religious, spiritual, and social symbol throughout recorded history.  Generally, hands symbolize power, strength, direction,  and blessing.  In Michaelangelo's painting, God's hand is sending the spark of life to Adam.  The hand of God often represents the power of God.  A single raised hand generally represents a blessing but, in Islam, it represents the five basic principles of Islam.  A person with a hand on his chest usually represents submission to God.  Clasped hands can represent prayer or pleading.  A hand emerging from a cloud is another symbol of divine power or intervention.  The "hand of the Egyptians" represents the joining of male and female forces.  A well know ancient Egyptian painting shows the sun above with hands coming out of the rays of light and moving to those below.  There have been a number of suggested interpretations.  I think, as do some others, that it represents the power of the Spirit Sun, i.e. God's Light, coming down to bless those below.