The sloka we are going to discuss today is a very simple and well known sloka.
Gururbrahma guruvishnu gururdevo maheshwarah
guruh saakshaat param brahma tasmai sree gurave namaha
Explanation -- Guru is brahma ,guru is vishnu and shiva. He is direct brahman alone. Thus he is everything , he is the person who is ever established in brahman. The world is the effect the cause or substratum being brahman. Thus the guru is the world and everything in it too. He is all pervading, present everywhere. Displeasing the Guru is equal to displeasing god.
To such a guru I offer my prostrations.
The 4th sloka in guru gita is in the same lines of the earlier slokas.
Sthaavaram jangamam vyaaptham yat kinchit sacharaacharam
tatpadam darshitham yena tasmai sri gurave namaha
sthaavaram -- Not moving
jangamam -- moving
vyaaptham -- pervading
sacharaacharam -- in living and non- living
Brahman is from which world comes, world lies and the world ends.Brahman is the cause whose effect is the world.It is the substratum of the world.As the mud is the cause whose effect is the pot. This causation theory which explains the effect of world,where the brahman is the cause is only from an ignorant persons perspective.The rope was never a cause for the illusion of snake but Its the ignorance which causes the superimposition of the snake over the rope. So from an ultimate view point brahman it is not the cause of the world.
Thus Guru who is Brahman himself is said to be all pervading .Brahman is present in the world in both living and non-living.
To such a guru who shows me the path to realization I offer my Prostrations.