I'm going to go with a "what" and not a "who". (For only Horton Hears a Who!)
Now, it may be because I'm a bit tipsy, but I figure since Angelic beings appear to be pure energy creatures (see transformation accounts) the spirit of God must be some type of dynamic energy source ... kinda similar to "the force" of Star Wars. Once received, it has to be harnessed and cultivated by the recipient's faith in its presence.
You can also 'grieve' the Spirit. (Interesting human quality applied here). Similar to Luke Skywalker telling Yoda, "I can't believe it", when Yoda lifted the X-Wing out of the swamp water. Yoda replies, "And that's why you fail".
"If you have faith the size of a mustard seed, you will say to this mountain, move, and it will move." ..... "You of little faith why did you doubt?" ( see the walking on water incident). That should ring some bells.
Star Wars was a play on religion in case you hadn't noticed. A very very insightful one at that.