It is like the light manifesting the lamp. So even at a first hearing of Om, the Lord is cognizable, like the sun by its light.
When the yogi has thus understood the relation of expression (Om) and expressed (the Lord), what is the discipline which attracts the grace of the Supreme Lord to him? To explain this the sutra says: ‘Repetition of it and meditation upon its meaning.’ Repetition of Om which is the expression of the Lord is called japa, and it is repetition mentally or in a low voice. The repetition is made of Om considered as of three measures (A, U and M) or considered as of three-and-a-half measures (A, U, M and the soundless). Meditation upon its meaning: meditation is contemplation on the Lord, the meaning, held steady by the Om which is his expression. The meaning is thus implanted in the mind (buddhi).
Yogis who are thus doing both (Om-repetition and meditation on the meaning) attain one-pointedness of mind. And that attainment of one-pointedness is a result of worship.
There is a traditional verse:
Through Om-repetition let him practise yoga,
Through yoga, let him set his mind on Om;
By perfection in Om-repetition and in yoga
The Supreme Self shines forth clear.