This metaphorical explanation in a few verses actually has a deep meaning about life, about how we connect with life, how we depend on the Universe, and how we affect the whole Universe.
Just this concept that Kṛṣṇa explains in a few verses here is explained in detail in the Chāndogyopaniṣad. Our relationship with the activity of Nature is a very deep one. Our actions are like oblations offered in a fire sacrifice. Our activities are not just movements of the limbs. When we perform a yajña, a fire sacrifice of enriching the Source, the Cosmic Energy we pour various offerings into the fire. We do so to tap the Cosmic Energy and to flow in tune with Existence, with Nature.
The subtlest, most powerful and all-pervasive Cosmic Energy is invoked through the slightly less subtle air element when we chant the mantra and we connect and enrich the still, less subtle fire energy through the fire ritual. Energy is then transferred to water, a grosser energy, and then the water in the pots is poured over plants, idols and humans as well as the earth, which is the grossest form of energy. When we chant the mantra, it is a very powerful way to enrich the world, through our integrity and authenticity. You take the responsibility for the words, and for making the mantra into reality. When you take the responsibility for the words you utter and start working, you enrich the world mystically and physically, metaphysically and physically.
A physical action is a gross expressed action, something that can be seen on the physical plane. Thoughts, mental actions, are subtler unexpressed actions, and they cannot be seen on the physical plane.
Enriching is the way in which you relate with the expressed component of God, the expressed part of God. Integrity and Authenticity are the ways in which you relate with the unexpressed, avyakta part of God. Responsibility and Enriching are the ways in which you relate with vyakta, the expressed part of God.
When we perform a sacrifice, we perform certain invocations to the higher energies. So, we attract corresponding effects for our actions. Our actions are like offerings in a sacrifice. When the actions are in tune with tattvas of integrity, authenticity, responsibility and enriching, which is the flow of Existence, it is like offering ghee (clarified butter) into the fire. When we do not flow in tune with Existence, it is like offering mud into the fire. You know the kind of smoke comes out of the fire when you offer ghee and the kind of smoke that comes out when you offer mud. Just like you can determine the quality of the offering you gave to the fire from the quality of the smoke, the result of your actions can be determined from the quality of your actions. The quality of the end result is based on our input, our offerings, our enriching.
Integrity and Authenticity are the right ways to relate with the unexpressed part of God, avyakta. Responsibility and Enriching are the right ways to relate with the expressed part of God, the world, vyakta. If you do not enrich, you actively create a selfish pattern and your offerings bring that same result. Be very clear, either you give or you swindle. There is no middle.
Kṛṣṇa says that rains become possible from the enriching sacrifice, yajñād bhavati parjanyo and the enriching sacrifice is born of actions, yajñaḥ karma-samudbhavaḥ (3.14).
Rain is a grosser form of energy that is activated by the subtler unexpressed energies which are influenced by our authenticity in actions and integrity in words, thoughts and vibrations.
Rain is the cause, the source which is responsible for the growth of food grains. Food is the enrichment needed to sustain our bodies and minds, which give rise to further authentic action and integrated thinking. So, you see this cycle now, of how the subtle energy, avyakta, the unexpressed part of God manifests itself in the grosser world as vyakta, the expressed part of God, and how the actions in the grosser world affect the subtler elements.
If we just understand this, we will realize that everything that we do and experience is caused by our own actions. We realize that we are the source of everything, and therefore responsible for everything that is happening. We invite our destiny. As we sow, so shall we reap.
Enriching is sowing the seed for the fruit to happen. Integrity is the root, authenticity is the tree, responsibility is the fruit, enriching is sharing the fruit to create more fruits. Every person who eats the fruit is responsible for sowing the seed for more fruits to happen.
Understand, this is what Kṛṣṇa says, ‘O Pārtha, he who does not adopt the prescribed, established cycle lives a life full of sins, aghāyur idriyārāmo. Rejoicing in sense gratification, he lives a useless life, moghaṁ pārtha sa jīvati (3.16).’
When you do not enrich every person with the fruit of enriching after constantly being enriched by the sacrifice of the Existence, the Supreme, your life becomes full of sins and you live a useless, incomplete life. That in turn brings the cycle of more and more incompletions!
If you are rich, be the ground on which the seed can be sown. If not, at least pour water for the seed to become a tree. If not, at least be a gardener to weed out the unnecessary things for the seed to become fruit again. Either offer your time, talent, or treasure. If you have eaten the fruit, it is your responsibility to make the seed again into a fruit. After eating the fruit, be responsible to sow the seed and make sure the seed again brings more fruits for more people to enjoy.