tamasas capi pascimah
nadyo nada-nadinam ca
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The back of the Lord is the place for all kinds of frustration and ignorance, as well as for immorality. From His veins flow the great rivers and rivulets, and on His bones are stacked the great mountains.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In order to defy the impersonal conception of the Supreme Personality of Godhead, a systematic analysis of the physiological and anatomical constitution of His transcendental body is given here. It is clear from the available description of the body of the Lord (His universal form) that the form of the Lord is distinct from the forms of ordinary mundane conception. In any case, He is never a formless void. Ignorance is the back of the Lord, and therefore the ignorance of the less intelligent class of men is also not separate from His bodily conception. Since His body is the complete whole of everything that be, one cannot assert that He is impersonal only. On the contrary, the perfect description of the Lord holds that He is both impersonal and personal simultaneously. The Personality of Godhead is the original feature of the Lord, and His impersonal emanation is but the reflection of His transcendental body. Those who are fortunate enough to have a view of the Lord from the front can realize His personal feature, whereas those who are frustrated and are thus kept on the ignorance side of the Lord, or, in other words, those who have the view of the Lord from the back, realize Him in His impersonal feature.