In Siman 4 we begin to learn the halachos of washing one's hands. (This siman does not cover washing one's hand for food.).
Regarding washing in the morning upon awakening, there is a dissagrement among the Rishonim.
The Rosh writes that since one's hands are 'busy' during the night and most assuredly have touch unclear areas of one’s body during the night, one must wash upon awakening..
The Rashba writes that after sleep we are deemed to be a 'new creation'. We must thank Hashem for this. To do so we must make certain preperations. The Rashba writes that it was simply established that we wash our hands in the morning in preparation for prayer, similar to a Kohen, who washes from the kiyor prior to performing his avodah.
There are a numerous differences between these two reasons as we will see in this siman.