Guru Stotram 11

"Na Guror-adhikam tattvam na Guror-adhikam tapah
Tattva-gyanat-param nasti tasmai Shri Gurave Namah"

There is no higher truth than the Guru, no higher penance than (service to) the Guru, and there is nothing higher than Realisation of the Knowledge of the truth imparted by the Guru. My salutations to that glorious Guru, who is himself that very timeless truth (and who has taken up a form to bless his disciples like us with real knowledge).