Nimittam aprayojakam prakrteenaam varana-bhedas tu tatah ksetrikavat
The incidental cause does not initiate natural evolution into activity but removes the obstacles like a farmer irrigating a field.
Taken into relation with the previous verse, Nature’s abundant flow of energy can be channeled by the Yogi in order to remove obstacles in his /her path of evolution. This is the reason behind constant regular Sadhana, a routine discipline to build up one’s inner resolve and internal energy resources in order to cultivate one’s innate consciousness towards perfection and emancipation.
There are three eternal principles in Yoga: Ishwara (Paramatman, the Eternal Witness, the Seer), the Jiva (the individual soul) and Prakriti (Nature, constant flux and dynamism). Think of this as God the Father (Ishwara), the Son (the Self-realized Jiva) and the Holy Spirit (when Nature is channeled to remove obstacles in order to realize one’s ‘Son-ship’).