The continuous repetition of Pranava with the meditation on its meaning is the means to attain Samadhi.
tad = its
tad = its
bhāvanam = absorption
The repetition of Pranava and the meditation of its meaning. The meaning of Pranava is God. In this manner, Samadhi is reached.
Commentary by Maharishi Vyasha
Its repetition and the comtemplation of its meaning
The repetition of Pranava and the contemplation on its connotation-God. By this manner, One who has sought recourse to the repetition and the absorption of its meaning attains Samadhi as declared (by Vishnu Purana): After repetition, one should go for meditation and after meditation, he again go for repetition. Attaining perfection in this manner, the supreme spirit lightens.
Commentary by Swami Vivekananda
The repetition of this (Om) and meditating on its meaning (is the way).
Why should there be the repetition? We have not forgotten that theory of Samskaras, that the sum-total of impressions lives in the mind. Impressions live in the mind, the sum total of impressions, and they become more and more latent but remain there, and as soon as they get the right stimulus they come out. Molecular vibration will never cease. When this universe is destroyed all the massive vibrations disappear, the sun, moon, stars, and earth, will melt down, but the vibrations must remain in the atoms. Each atom will perform the same function as the big worlds do. So the vibrations of this Chitta will subside but will go on like molecular vibrations, and when they get the impulse will come out again. We can now understand what is meant by repetition. It is the greatest stimulus that can be given to the spiritual Samskaras. “One moment of the company with the Holy makes a ship to cross this ocean of life.” Such is the power of association. So this repetition of Om and thinking of its meaning is keeping good company in your own mind. Study, and then meditate and meditate, when you have studied. The light will come to you, the Self will become manifest. But one must think of this Om, and of its meaning too. Avoid evil company, because the scars of old wounds are in you, and this evil company is just the heat that is necessary to call them out. In the same way, we are told that good company will call out the good impressions that are in us, but which have become latent. There is nothing holier in this world than to keep good company because the good impressions will have this same tendency to come to the surface.
Commentary by Sri Osho
REPEAT AND MEDITATE ON AUM.
Repeat and create all around you the sound of aum, but don’t be lost in it. It is such sweet sound you will be lost. Remain alert – remain more and more alert The more sound goes deeper, you become more and more alert; so the sound relaxes your nervous system, but not you. The sound relaxes your body, but not you. The sound sends your whole body and the physical system into sleep, but not you.
Then double process has started: the sound drops your body to a restful state and the awareness helps you to rise to the superconscious. Body moves to the unconscious, becomes a zombie, fast asleep, and you become a superconscious being. Then your body reaches to the bottom and you reach the peak. Your body becomes the valley and you become the peak. And this is the point to be realized.
Repeat and meditate.