Yoga Sūtra Chapter Four verse 3

निमित्तमप्रयोजकं प्रकृतीनांवरणभेदस्तु ततः क्षेत्रिकवत् ॥३॥

nimittam-aprayojakaṃ prakṛtīnāṃ varaṇa-bhedaḥ tu tataḥ kṣetrikavat ||3||

The instrumental cause is not the initiator of the process of matter,
but divides the surrounding, hence like a farmer.

nimitta - instrumental cause; cause, motive, ground, reason; instrumental or efficient cause; a cause that concurs in, or is elevated to, the production of something more noble than itselfaprayojaka - not the initiator; not causing or effecting, aimlessprakṛti - the original producer of the material world; nature or process of matter; nature, character, constitution, temper, dispositionvaraṇa - surrounding, enclosingbheda - dividing, breaking, splitting, cleaving, rending, tearing, piercing; distinction, difference, kind, sort, species, variety; separation, division, partition, part, portiontu - moreover; buttatas - hence, from thatkṣetrika - like a farmer; relating to a field, having a field, agrarian; the owner of a field; a farmer, cultivator

Commentaries and Reflections

Commentary by T Krishnamacharya:

Commentary by TKV Desikachar:

“Krishnamacharya’s teaching is a Nimitta Kāraṇa
– Where you discover your own way.”

Commentary by S Ramaswami:

“What causes this change?
For any activity the causes are usually two or three:
– Nimitta – Efficient cause (i.e. weaver, potter)
– Upadāna – Material cause (i.e. threads, dye, clay)
– Kāraṇa – Accessories (i.e. loom, wheel)
It is possible without the third.
Vedānta attributes the first two to Brahman. Like a spider producing from itself a web to spin a web.
However according to Yoga, transformation from one being to another at the end of one Janma is not due to the presence of Brahman.Then how does it take place?
The farmer is diverting the water in a particular direction by merely removing obstacles.
The Prakṛti flows by itself to go to a higher or lower to have more Sattva or Tamas. All we can do is keep removing the bunds.
The Prakṛti flows by itself.
This analogy can be applied to manifestations of Prakṛti  within the individual.
In Prāṇāyāma when we remove the obstacles the Prāṇa flows by itself.
With regards to the Nāḍī when the Granthi are pierced Kuṇḍalinī flows by itself.
Nimitta here usually means Dharma or Sattva and Adharma or Tamas.
Right action of wrong action are not caused they don’t create something new. The flow is the Guṇa or Prakṛti  and depending where the flow is opened or closed comes Sattva or Tamas.
Puruṣa nor Īśvara have no part in this process at all.
However this is still within the realms of transformation and is thus only a temporary state.”

Commentary by Paul Harvey:

Nimitta is seen as the agent for change, as if a farmer.
Everything required is there, along with the intelligence.
You just have to find the intelligence to find the intelligence.
So verse 3 talks about the tools, materials and intelligence.”