Sravana -Hearing/learning Vedanta Vakya methodically from a competent teacher.
Manana - Reflecting upon these teachings and their essence (which is Brahman) repeatedly, till there all doubts are resolved.
nididhyAsana - Devoted, total and undisturbed 'internal' contemplation (meditation) on the essence of the Vedanta Vakya perceived through shravaNa and manana.
It thus becomes clear that shravaNa plays a very important part in Brahma Sakshatkara, as without shravaNa, there cannot be manana or nididhyAsana and hence brahma jnAna. Hence shravaNa is the reason or primary cause for brahma jnana. This is aptly described by Sri Samkshepa ShArirakAchArya as below:
vedantabhUmigatamadarapAlitaM cha |
sannyAsinA paradR^ishA guruNopadiShTam
sAkshAnmahavachanameva vimuktihetuH ||
Of the three, shravaNa is of great importance as:
paripakvamateH sakR^itChrutaM janayedAtmadhiyaM shrutervachaH |
For some uttamAdhikari-s, even in the absence of mana and nididhyAsana, shravaNa from a Sadguru alone can lead to aparokSha jnAna. But on the other hand, in the absence of shravaNa, mere manana or nididhyAsana cannot lead one to aparokSha jnAna. Thus by anvaya-vyatireka (accordance and discordance), the primary importance of shravaNa in realization becomes established. Sri Anandagiri, in his vyAkhyAna, clearly states the angAngi relation, establishing angitva of shravaNa and angatva of manana-nididhyAsana. Some erroneously understand these three practices to be mutually exclusive – one undergoes shravaNa for a year, then manana for two years and discards these two to undertake nididhyAsana. This is incorrect as clarified by Bhagavan Bhashyakara himself. Let's say one listens to the vedAnta vakya and its essence from a Sadguru for an year and does no manana at all for this period. By the time of the second year which is allocated for manana, he would have forgotten all the teachings heard for a year due to absence of manana along with shravaNa. Similar is the case with nididhyAsana, if one undertakes the same after three years of exclusive indulgence in shravaNa and manana. If one sows seeds and then begins to water after an year, how can he expect the sprouting of the already dry seed, and hope to eat the fruit from the tree? These three are complimentary to each other and should be undertaken together. They cannot be isolated as individual practices undertaken exclusively, one after another.
The Sannyasi is the primary adhikAri for shravaNa, manana and nididhyAsana [sannyasya shravaNam kuryAt].