Good soil, clean water, and sunlight — give a seed these three and the harvest does not take long. Krishna names the three conditions for knowledge: shraddha (faith), tatparata (sincere dedication), and indriya-samyam (mastery over the senses). Whoever has all three gains knowledge, and having gained it, attains supreme peace quickly.
The word 'achirena' — quickly, without delay — is full of encouragement. Krishna is not describing a path that takes forever. When the preparation is right, the result comes swiftly. The delay is never on knowledge's side. It is always on the seeker's side — and these three qualities clear the way.