It is said:

Simultaneously born wisdom of absolute truth comes only from the handprint of the accumulation of merit, the purification of obscurations, and the blessings of the Guru.   

Someone who thinks that there is a method other than this, is a foolish man.

The developing and completion stages are not able to liberate by the essence of their path – they depend on conduct and advantageous circumstances.  

Guru yoga is only the essence of the path, so the realisation of the unconditioned nature is born in the mind and one becomes liberated.  

Guru yoga is more profound than all other paths. 

— Longchenpa