In plain words
Each of these cannot be separated from the other; all three are bound by an inseparable relation. Karma flows on ceaselessly, like a river's current. All sentient and insentient things in creation, caught in the force of this current of karma, revolve ceaselessly in the wheel of saṃsāra. Karma means motion. Space is the field within which motion is possible; what moves within it is air. From the motion of air, fire arises. Everyone knows that fire is produced by the friction of these two. And also, as long as the motion of inhalation and exhalation continues, living beings' bodies retain warmth -- this is another proof. There is no need to say separately that warmth is a characteristic of fire. That life arises from fire is strongly proven by the fact that clouds arise from the sun's radiance.
Particles of water, through union with other elements, undergo solidification, and from the earth herbs arise -- this matter is clear to us. From herbs comes food; from food comes vital energy; and from that a person arises. All of this is the Creator's own way of working. This is the purport of the Śruti.
That is, all of these things happen in succession, because of the effect of motion and of transformation. There is no need to say separately that there must be, as the foundation for so great a current of motion, one unmoving thing. That very unmoving supreme reality alone is called Ātma, or Para-Brahman. The Supreme Lord's own powers of Jñāna, will and action are themselves spandana; and spandana itself is called karma. Between creation and karma there exists an inseparable relation. It is because of the effect of this very karma that Brahmā, Viṣṇu and Maheśvara, as forms, come to be the agents of creation, preservation and dissolution. All planetary motions, and all other worldly affairs besides, occur subject to karma.