Sutra 26
Matter provides a dwelling place for the conditioned souls. This place is called, "the three dimensions of material space".
Commentary by Srila Bhaktivinoda Thakura
Matter provides a dwelling place for the conditioned souls. This place is called, 'the three dimensions of material space'. An example of material space is given in these words of the Svetasvatara Upanisad (4.6-7):
"Although the two birds are on the same tree, the eating bird is fully engrossed with anxiety and moroseness as the enjoyer of the fruits of the tree."
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If a person engages in the process of bhakti yoga and yet continues to engage in activities that are detrimental to spiritual progress, his spiritual progress will be very slow. This does not mean that a person must be completely free of all bad habits before he can even begin the process of bhakti yoga. For example, in the Philippines, one teacher saved many young people who were addicted to heroin and other drugs by teaching them the process of bhakti yoga. It took some time before they could completely give up all drugs; but eventually they did.
Siddhaswarupananda - Chris Butler Speaks
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The 'tree' here is the material dwelling place (the body) of the conditioned soul.
Many philosophers assert that the element earth is the resting place of the other material elements. This is described in the following words of the Mundaka Upanisad (2.1.3):
"From the Supreme Personality of Godhead are born life, mind, all the senses, ether, air, fire and water. All these rest on the element earth."
In a previous mantra (Mundaka Upanisad 2.1.2) it is said:
"The Supreme Personality of Godhead is effulgent and transcendental. He is unborn. He is present everywhere in the material world. He is within and without everything. His form is not material. His life-force is not material. His mind is not material. He is supremely glorious. He is greater than the immortal spirit souls."
"O material potency of the Lord, you are the resting place of the entire universe."