Bg 7.1

sri-bhagavan uvaca
mayy asakta-manah partha
yogam yunjan mad-asrayah
asamsayam samagram mam
yatha jnasyasi tac chrnu

Word for word: 
sri-bhagavan uvaca — the Supreme Lord said; mayi — to Me; asakta-manah — mind attached; partha — O son of Prtha; yogam — self-realization; yunjan — practicing; mat-asrayah — in consciousness of Me (Krishna consciousness); asamsayam — without doubt; samagram — completely; mam — Me; yatha — how; jnasyasi — you can know; tat — that; srnu — try to hear.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
The Supreme Personality of Godhead said: Now hear, O son of Prtha, how by practicing yoga in full consciousness of Me, with mind attached to Me, you can know Me in full, free from doubt.

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In this Seventh Chapter of Bhagavad-gita, the nature of Krishna consciousness is fully described. Krishna is full in all opulences, and how He manifests such opulences is described herein. Also, four kinds of fortunate people who become attached to Krishna and four kinds of unfortunate people who never take to Krishna are described in this chapter.

In the first six chapters of Bhagavad-gita, the living entity has been described as nonmaterial spirit soul capable of elevating himself to self-realization by different types of yogas. At the end of the Sixth Chapter, it has been clearly stated that the steady concentration of the mind upon Krishna, or in other words Krishna consciousness, is the highest form of all yoga. By concentrating one’s mind upon Krishna, one is able to know the Absolute Truth completely, but not otherwise. Impersonal brahma-jyotir or localized Paramatma realization is not perfect knowledge of the Absolute Truth, because it is partial. Full and scientific knowledge is Krishna, and everything is revealed to the person in Krishna consciousness. In complete Krishna consciousness one knows that Krishna is ultimate knowledge beyond any doubts. Different types of yoga are only steppingstones on the path of Krishna consciousness. One who takes directly to Krishna consciousness automatically knows about brahma-jyotir and Paramatma in full. By practice of Krishna consciousness yoga, one can know everything in full – namely the Absolute Truth, the living entities, the material nature, and their manifestations with paraphernalia.

One should therefore begin yoga practice as directed in the last verse of the Sixth Chapter. Concentration of the mind upon Krishna the Supreme is made possible by prescribed devotional service in nine different forms, of which sravanam is the first and most important. The Lord therefore says to Arjuna, tac chrnu, or “Hear from Me.” No one can be a greater authority than Krishna, and therefore by hearing from Him one receives the greatest opportunity to become a perfectly Krishna conscious person. One has therefore to learn from Krishna directly or from a pure devotee of Krishna – and not from a nondevotee upstart, puffed up with academic education.

In the Srimad-Bhagavatam this process of understanding Krishna, the Supreme Personality of Godhead, the Absolute Truth, is described in the Second Chapter of the First Canto as follows:

srnvatam sva-kathah Krishnah
punya-sravana-kirtanah
hrdy antah-stho hy abhadrani
vidhunoti suhrt satam

nasta-prayesv abhadresu
nityam bhagavata-sevaya
bhagavaty uttama-sloke
bhaktir bhavati naisthiki

tada rajas-tamo-bhavah
kama-lobhadayas ca ye
ceta etair anaviddham
sthitam sattve prasidati

evam prasanna-manaso
bhagavad-bhakti-yogatah
bhagavat-tattva-vijnanam
mukta-sangasya jayate

bhidyate hrdaya-granthis
chidyante sarva-samsayah
ksiyante casya karmani
drsta evatmanisvare

“To hear about Krishna from Vedic literatures, or to hear from Him directly through the Bhagavad-gita, is itself righteous activity. And for one who hears about Krishna, Lord Krishna, who is dwelling in everyone’s heart, acts as a best-wishing friend and purifies the devotee who constantly engages in hearing of Him. In this way, a devotee naturally develops his dormant transcendental knowledge. As he hears more about Krishna from the Bhagavatam and from the devotees, he becomes fixed in the devotional service of the Lord. By development of devotional service one becomes freed from the modes of passion and ignorance, and thus material lusts and avarice are diminished. When these impurities are wiped away, the candidate remains steady in his position of pure goodness, becomes enlivened by devotional service and understands the science of God perfectly. Thus bhakti-yoga severs the hard knot of material affection and enables one to come at once to the stage of asamsayam samagram, understanding of the Supreme Absolute Truth Personality of Godhead.” (Bhag. 1.2.17–21) Therefore only by hearing from Krishna or from His devotee in Krishna consciousness can one understand the science of Krishna.