Guru Brahma Guru Vishnu
Guru Devo Maheswarah
Gurusakshat Parambrahma
tasmai shree Guruve namah

Teachers all
The one who creates
The one who sustains
The one who dissolves
Disperses learning

All that you witness
The Creation around are teachers too
The One that imparts in form as a Master too
The Eternal Brahman
Salutations to all

A simple mantra but what depths!!
The jnani who experiences the Truth, the one who sustains it for posterity are teachers too.