gām āviśya ca bhūtāni
dhārayāmy aham ojasā
puṣṇāmi cauṣadhīḥ sarvāḥ
somo bhūtvā rasātmakaḥ

Translation of Bhagavad Gita 15.13

I enter into each planet, and by My energy they stay in orbit. I become the moon and thereby supply the juice of life to all vegetables.

Commentary by Sri A.C. Bhaktivedanta Swami Prabhupada of Gaudiya Sampradaya:

It is understood that all the planets are floating in the air only by the energy of the Lord. The Lord enters into every atom, every planet, and every living being. That is discussed in the Brahma-samhita. It is said there that one plenary portion of the Supreme Personality of Godhead, Paramatma, enters into the planets, the universe, the living entity, and even into the atom. So due to His entrance, everything is appropriately manifested. When the spirit soul is there, a living man can float on the water, but when the living spark is out of the body and the body is dead, the body sinks. Of course when it is decomposed it floats just like straw and other things, but as soon as the man is dead, he at once sinks in the water. Similarly, all these planets are floating in space, and this is due to the entrance of the supreme energy of the Supreme Personality of Godhead. His energy is sustaining each planet, just like a handful of dust. If someone holds a handful of dust, there is no possibility of the dust’s falling, but if one throws it in the air it will fall down. Similarly, these planets, which are floating in the air, are actually held in the fist of the universal form of the Supreme Lord. By His strength and energy, all moving and nonmoving things stay in their place. It is said in the Vedic hymns that because of the Supreme Personality of Godhead the sun is shining and the planets are steadily moving. Were it not for Him, all the planets would scatter, like dust in air, and perish. Similarly, it is due to the Supreme Personality of Godhead that the moon nourishes all vegetables. Due to the moon’s influence, the vegetables become delicious. Without the moonshine, the vegetables can neither grow nor taste succulent. Human society is working, living comfortably and enjoying food due to the supply from the Supreme Lord. Otherwise, mankind could not survive.

The word rasatmakah is very significant. Everything becomes palatable by the agency of the Supreme Lord through the influence of the moon.

Commentary by Sri Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

Entering the earth (gam) by my own sakti (ojasa), and being situated there, I maintain the moving and non-moving entities (bhutani). Becoming the sweet-juiced moon, I cause plants such as rice to increase and grow.

Commentary by Sri Ramanuja of Sri Sampradaya:

15.13 Entering the earth I uphold all beings by My strength, namely, by My irresistible power, Likewise, becoming the Soma consisting of the juice of the nectar, I nourish all herbs.

Commentary by Sri Sridhara Swami of Rudra Sampradaya:

Continuing Lord Krishna states that He enters into every particle of earth with His energy, prevading over all the Earth with His prowess and supports all moving and non-moving jivas or embodied beings. He, Himself is the luminousity of moonlight which nourishes all herbs and crops such as rice, fruits an grains.

Commentary by Sri Madhvacharya of Brahma Sampradaya:

The word gam stated by Lord Krishna means Earth and within the earth.

Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

The all pervading potency of Lord Krishna is in the Earth by which He permeates sustaining and nourishing all movable and immovable jivas or embodied beings by His ojasa or irresistable potency and bmanifesting as the ambrosial nectar of the moon he nourishes all plant life such as herbs, vegetables, fruits and grains.

Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

15.13 Ca, and; avisya, entering; gam, the earth; aham, I; dharayami, sustain; bhutani, the beings, the world; ojasa, through (My) power, the power that belongs to God and is free from passing and attachment, (and) which has penetrated the earth to support it, and owing to which the heavy earth does not fall and does not crumble. There is a similar mantra: ‘By which the heaven is made mighty, and the earth firm’ (Tai. Sam., and also, ‘He supported the earth’ (op.cit.,, etc. Hence, it has rightly been said, ‘Entering the earth I sustain the moving and non-moving beings.’ Moreover, pusnami, I nourish, I make healthy and full of the sweet flavour of juices; sarvah, all; osadhih, the plants-paddy, barley, etc.; bhutva, by becoming; somah, Soma; rasatmakah, which is of the nature of sap. Soma consists of all the juices; it is the source of all juices. Indeed, it nourishes all plants by infusing its own juice into everything. Besides,

Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:

15.12-14 Yad aditya-etc. upto caturvidham. While clarifying the role [of the Lord] as the Creator, Sustainer and Destroyer – a role that has been indicated in the Tenth Chapter – by [the description of Him as identical with] the triple luminories like the sun etc., our venerable preceptor has rightly said : The present passage declares that the power, the pentad of elements has [both] collectively and individually, to sustain the world, is the Absolute power of the Bhagavat Himself. For instance : The sunlight has the power of illumining and sustaining, because the twin elements of the fire and the earth are one [with the Bhagavat]. This has been started by the twin hemistitches ‘[That light] which is found in the sun etc.’ and ‘And by penetrating the earth etc.’ The moon-light is illumining and nourishing because of its assoication of the elements of the earth, the water and the fire [with the Bhagavat]. That has been stated by the portion ‘[That light] which is in the moon’ and by the hemistitch ‘Being the sapful moon I nourish all plants’. The light of fire is, however, of the nature of illumining, parching, burning, sweating and ripening (or cooking). It is so because of the association of the elements, the earth, the water, the fire and the wind [with the Bhagavat]. The same has been said here by the portion, ‘[That light] which is in the fire’ and also by the [entire verse] ‘I, being the digestive fire etc.’ But the [element] ether is no doubt all pervaisve (inclusive), because it is of the form of room which is nothing but awareness. Therefore, having so far explained the nature [of the Absolute Self] as the object of knowledge, now, with a view to show the Self to be conscious of the freedom that remains as a background (or substratum) of that very nature of object of knowledge; to be of transcending nature; to be the Supreme Lord; to be independent in all knowledges; and to be the Creator of all; [the Lord] says –

Sanskrit Shloka Without Transliteration Marks:

gam avisya ca bhutani
dharayamy aham ojasa
pusnami causadhih sarvah
somo bhutva rasatmakah

Sanskrit to English Word for Word Meanings:

gām — the planets; āviśya — entering; ca — also; bhūtāni — the living entities; dhārayāmi — sustain; aham — I; ojasā — by My energy; puṣṇāmi — am nourishing; ca — and; auṣadhīḥ — vegetables; sarvāḥ — all; somaḥ — the moon; bhūtvā — becoming; rasa-ātmakaḥ — supplying the juice.