Krishna completes the meditation technique. Whoever utters the single syllable Om — the sound-symbol of Brahman — while remembering God, and departs the body in this state, reaches the supreme goal: moksha.
Om is the seed-sound of all creation in the Vedic tradition. Just as hearing a person's name instantly brings their face to mind, chanting Om brings the fullness of Brahman into awareness. One small syllable contains the essence of the entire universe.
This is why every puja, every mantra, every auspicious act in tradition begins with Om. The Gita affirms what the Upanishads have long taught: this tiny syllable is the doorway to the infinite.