In plain words
What is sacred is humanness. What is worth living is humanness. Without letting go of the goal, to make humanness worthwhile is his duty. The union of body, mind and Ātma is humanness. These three reveal man's nature. They take humanness to a high state. One meaning of this is that these very three are doing, knowing and being. Doing means: Śarīramādyaṃ khalu dharmasādhakam. Through this body alone all the acts of Dharma go on being done. Without the body, no acts of Dharma could be done at all. That is why this body is the instrument fitted for doing all karmas.
Next, the second: the mind. Saṅkalpavikalpātmakaṃ manaḥ. At every moment it is bound up with resolving and doubting. Manomūlamidaṃ jagat. The whole world, all of it, exists only as made of the mind. No object, no person, no subject without the mind is to be seen in it. Weighing good and bad, too, takes place through the mind alone. Examining the eternal and the passing, too, takes place through the mind alone. So one meaning of it is that the mind is knowing.
Then the Ātma. It is the form that is eternal, Satya, pure, selfless and full of light. By no combining does it undergo change. It shines as the supreme Light in man's inner self. The śāstras call that very thing Divinity too. The sacred śāstras and histories of the people of Bhārata have gone on teaching nothing but this inner self. The śāstras have also taught that God is the embodiment of the Ātma. The Upaniṣads teach that He dwells in the cave of the heart as the embodiment of the Ātma. The Bible has declared that only when the heart is pure is it possible to attain Divinity. The Qur'ān of the Muslims has taught that to do holy deeds and keep the heart in a pure state is itself the Divinity that is divine. Guru Nānak taught that humanness is shown forth by good feelings, good karmas and good conduct, saying that the heart is what matters most. In short, the essence of all religions and the goal of all paths has gone on showing forth just this: the purity of the heart. So Prema and Satya do not belong merely to the body. They belong to the heart.
Man is truly the embodiment of the Ātma. But forgetting this true form of his, people grow elated over these fleeting, petty, worldly pleasures and riches, and are forgetting God.