In plain words
Attachment to the body is the root cause of the unrest, discontent, hardships and sorrows that people suffer. Treat the body as an instrument, keep the indweller as your goal, and lead your daily life that way.
The principle that is the basis
Every object has one substance as its basis. This whole world has come from a single basis. If you let go of that basis, you will have lost everything. This is a silver vessel. All these forms and names began from the silver that is their basis, did they not? If you cast away the silver that is their basis, these forms and names have no value at all. You can break up a plate and turn it into a spoon. You can break up the spoon and make a small cup. So all forms and names are bound to change, bound to die! But the substance that is the basis of forms and names never changes. It does not die.
the Eternal One who has neither death nor birth, without beginning, middle or end, the beginningless One; He Himself, unborn, undying, unslain, abides everywhere in the form of the Ātma.
What is the basis of the body, of prāṇa, of the mind? For all of them the one Divinity alone is the basis. By the sun's rays the water of the sea turns into vapour. The vapour takes the form of clouds, and when a cool wind blows on those clouds they fall down as drops of rain. Those very raindrops take the form of streams and flow back into the sea. That is to say, the water of the sea takes on all these forms and names and in the end merges back into the sea itself.
In the same way every living being and every object in this world has come from the one principle that is the basis. In the end they must all go back into that principle that is the basis. It is with this in mind that the Bhāgavatam said, “To go back to where it was born is the nature of every living being.”