In plain words
So only when we bring the mind along with the body and do service does it become divine yoga.
This is 'karmaṇyeva adhikāraste' in the Bhagavad Gītā. Your right is to karma alone. Do karma. The joy that is in this karma is not to be found in anything else. So when man brings the mind into the doing of karma and renders service through this mind, it takes shape as true sādhana. Sādhanas done without such a mind are wholly useless. The body is not real. It is only an instrument. But you must keep bringing the instrument into the thing called the mind and, through it, into action. That is why in Vedānta they have said, 'manayeva manuṣyāṇāṃ kāraṇaṃ bandha mokṣayoḥ'.
The body is made of the five elements; the body must fall one day without fail; the dweller in the body is free of sickness; reckoned rightly, for the dweller in the body birth and death and the marks of the bonds of delusion do not exist; see the truth: that dweller in the body is the God of gods; think it over in your mind: He is of the form of the Ātma.
We must recognise the principle of that dweller in the body. That divine principle called the dweller in the body is in everyone. So whomever you serve, you must believe that you are serving God. Through this service the mind becomes pure. The body too becomes worthwhile. If the mind does not become pure, there is no use in having a body.
A house of filth, a drudge's basket rotting in diseases, a tuber that is born and moves on, a thorn bush that cannot cross the ocean of worldly life, a quiver of arrows; rise and see: whenever we think of it, do not believe this body is lasting, O mind; take refuge at the feet of Hari!
So we must develop the principle of the mind well. We must let the mind experience its own true nature. The mind is always pure in itself. This cloth is white of itself. But because we use it in many ways, dirt gathers in it. When this dirt gathers, what do we do? We take it and give it to the washerman. The washerman takes away the dirt and brings it back. Then what do we say? We say, "The washerman has made it white and brought it." The washerman did not give it whiteness. He took away the dirt that was in it. This cloth has taken back its own true nature. The mind is by nature pure. Because it is made to experience this physical life, this physical dirt clings to it.