The lineage and master is one of the utmost important factors for one to be a Vajra master

I actually have permission from all of my teachers. […] These teachers that I just mentioned are not ordinary teachers but they were really important teachers, very important teachers in this century. I don’t think there will be more important or more authentic than these will appear, very difficult to appear, to have something like that. And then they did not tell me this privately, but they told me this in the public, in front of thousands of people, thousands of monks in Tibet. And it’s very necessary to have a lineage, and to have a great teacher, and to have the permission from the teacher to teach to others – the lineage and the master – to be a Vajra master. So that’s ones of the very important factors is to be a teacher. This is very important condition, for me, personally, to be a teacher of Longchen Nyingthik.

Hungkar Dorje Rinpoche, “GURU YOGA – Guru Yoga from Longchen Nyingthik Lineage”