Atisa says:
Friends, until you attain enlightenment you need a teacher, so follow a supreme spiritual friend.
Until you realize the natural state, you need to learn, so listen to his instructions.
All happiness is the teacher’s blessing, so always remember his kindness.
In one tantra it says:
Better than meditating on a hundred thousand deities
For ten million kalpas Is to think of one’s teacher for a single instant.
From: ‘The Words of my Perfect Teacher’