BG 15.16

This temple at Thiruvanvandur was reconsecrated by Nakula. Nakula, when he came here, enquired about this Kshetram and understood that the Lord here had appeared to sages Narada and Markandeya. We know that Narada is the son of lord Brahma. Because of a curse by his father lord Brahma, Narada is always on the move - triloka sanchari [त्रिलोक संचारी]! Lord Brahma first created Four sons [Sanaka, Sanatkumara, etc.] by his mental power, to assist him in his job of creations. Sage Narada did preach these Four a number of philosophical thoughts. As they gained gyana, they lost interest in this Universe. There are three types of behaviour - Karma bhavana [करमा भावन ], Brahma bhavana [ब्रह्म भावन ] and Ubhaya bhavana [उभय भावन]. In Karma bhavana, a person indulges only in worldly activities. In Brahma bhavana, one is always experiencing Brahmam [God] and is totally away from worldly activities. In Ubhaya bhavana, one is having both, like lord Brahma, doing worldly activities as well as meditating on Brahmam! Lord Brahma sought the help of his Four sons in his Karma or duty of creation. They refused to obey their father and said that they were interested only in Brahma bhavana. Lord Brahma was angry and he thought Narada was responsible and so, he cursed Narada that he would never stay at any one place and be always on the move! While thus wandering, once Narada came to this place. He worshiped the Lord here and prayed for Two boons, when the Lord appeared. One was that his wandering should stop so that he was able to compose one Purana from here. The other boon was that he should be blessed with Tatva Gyana or the knowledge about Brahmam and His creations. The Lord blessed Narada with the boons and Narda composed the mammoth Naradeeya Purana. Once sage Markandeya prayed the Lord that he should be able to see the great Pralayam, creation and have glimpse of all. Immediately, the Lord wide opened His mouth and Markandeya entered the body of the Lord through His mouth! Inside he could see all the Seven Worlds, Seven Seas, Seven Mountains, and everything. Afterwards he saw everything dissolved and only a tender small Banyan leaf, floating on the water. And, on that tiny leaf he could see the Lord lying as a small child sucking His toe! this also happened in this Kshetram! Learning these from the locals, Nakula decided to stay here and meditate on the Lord. Now, we will see sloka 15, a very important one:

sarvasya cāhaṃ hṛdi saṃniviṣṭo
mattaḥ smṛtir jñānam apohanaṃ ca
vedaiś ca sarvair aham eva vedyo
vedāntakṛd vedavid eva cāham 15.15

Sarvasya = of all the living beings, hrdi = hearts, aham = I [Sri Krishna], samnivista = well existing. The Lord says that He resided in the heart of every living being and commanded. Because of this existence, matta = by My [Sri Krishna's] control, smrti = rememberance, jnanam = percieving for the First time, apohanam = forgetfulness. By being in the heart of all living beings, the Lord is responsible for every living being's remembering, acquiring knowledge about what was perceived and also, forgetting! The Lord is in our body so that we are able to remember, to acquire knowledge and to forget what we knew! All these activities in every living being were controlled by Him! Sarvair vedai = by all Vedas, aham eva = I [Sri Krishna] am alone, vedya = described, vedanta = the final result of all Veda Karma [here vedanta does not mean Upanishads], krd = grant, vedavid = knowledgeable in vedas, ca = also, aham = I [Sri Krishna] am. The Lord alone grants the result of the many actions we do according to Vedas. The Lord alone knows Vedas. Though this sloka has got many detailed commentaries, we will see what are possible in the given duration. Shastras say 'antapravishta sasthaa jananam sarvatma' - sasthaa means Leader and indicates Sriman Narayana. He is pervading inside us. From inside He commands, controls and sustains everyone. This is what the Lord says in this sloka. Shastras say that our heart is like an inverted lotus bud! The Lord remains in this heart. Our body is Achit and in that is Jeevatman or Chit. Within this jeevatman is Paramatman! The combination of all the Three [Achit body, Chit atman and Paramatman] is called a living being or jeevarasi or bhuta! The Lord is thus present in all living beings. He is not merely present, but present and ruling! Space is also present everywhere; but it does not command nor rule the place it is! Smriti means something experienced earlier is remembered. Gyanam means the First time perception of anything. If we come to Thiruvanvandur for the First time, it is Gyanam. If we happen to visit again this place after some years, we remember the place. This is called Pratyajigya. That is, we remember after seeing the place or person again. But smriti, means, we do not visit that place again to remember, but without physically seeing the place or person, we remember. Gyanam, the First perception, can be of Four types: Pratyaksham, Anumanam, Shastra and Yoga. These are the ways one could perceive an entity and gain Gyana. Apohanam is forgetfulness. All these three - Gyana, Smriti and Apohanam - are in His control in every living being.
Swami Vedanta Desika in his Tatparya Chandrika uses 'eva [only]' in Three places in the Second part of the sloka. Sarva vedam eva aham vedya - the Lord is described by Vedas only. That means the Lord [God] can not be realized by other Gyana [pratyaksham and anumanam]. Vedas are called pramanam and the Lord is prameyam. In Brahma sootram, it is said 'shastra yonitvat' [1.1.3] - meaning this knowledge is only from Shastras. Aham eva vedya - all Vedas describe only the Lord [and none else]. But we come across the names of Indra, Varuna, Brahma, etc., are n't we? All those gods are the body of the Lord and He alone commands them. So all those words really mean the Lord only! Aham vedya eva - only by describing the Lord, will Vedas get merit. By telling that He alone knows Vedas it is implied that others like great sages Parashara, Agastya, etc., do not know vedas to the extent known by the Lord!