piṇḍe vāyv-agni-samśuddhe
hṛt-padma-sthāṁ parāṁ mama
aṇvīṁ jīva-kalāṁ dhyāyen
nādānte siddha-bhāvitām
piṇḍe - within the body; vāyu - by air; agni - and by fire; samśuddhe - which has become completely purified; hṛt - of the heart; padma - upon the lotus; sthām - situated; parām - the transcendental form; mama - of Mine; aṇvīm - very subtle; jīva-kalām - the Personality of Godhead, from whom all living entities expand; dhyāyet - he should meditate upon; nāda-ante - at the end of the vibration of oṁ; siddha - by perfected sages; bhāvitām - experienced.
According to Śrīla Śrīdhara Svāmī, the praṇava, or oṁkāra, has five parts: A, U, M, the nasal bindu and the reverberation (nāda). Liberated souls meditate upon the Lord at the end of that reverberation.