Meditative concentration makes the body light and agile

Question: Why do I feel my body is very light and floating when I read the Kṣitigarbha Sūtra?

Answer: This is a condition that arises from meditative concentration (samādhi). Once the mind becomes still, the qi and blood flow without obstruction and circulate smoothly, and the body becomes soft and light, as if it had no bones. Spiritual practice should be taken up while one is still young; when one's physical condition is good, the qi and blood become invigorated as soon as the mind is slightly stilled, and meditative concentration arises. Moreover, if a person's mind and thoughts are simple and have not been tainted by much defilement, it is easy for the mind to become still and attain samādhi. In addition, if one has the mind and conduct of a bodhisattva, has made aspirations and taken on responsibilities, and delights in helping others and practicing the bodhisattva path, then both the merit one attracts and the blessing power of the Buddhas and bodhisattvas play a great role. Those who have made aspirations and taken on responsibilities will benefit more sentient beings after they achieve accomplishment, so the blessing power of the Buddhas and bodhisattvas behind them is very great, and their own practice advances rapidly.
Those who have practiced for many years without progress should frequently examine what conditions they lack in various respects, and make up for them as much as possible. If it is because they have not yet brought forth bodhicitta, they should contemplate more on the suffering of sentient beings, contemplate more on the kindness of the Buddhas and bodhisattvas as well as the kindness of sentient beings, and frequently harbor a mind of gratitude and repaying kindness. By expanding the mind's scope and extending oneself to others, bringing forth bodhicitta will no longer be so difficult.

When meditative concentration arises, one will feel a separation of mind and matter, perceiving the unreality of matter, and thereby discover the truth and realize true principle. If mind and matter are not distinguished, the mind will be obscured by matter, unable to discover the true nature of matter, and foolishness will not be removed. Discovering the unreality and untruth of matter is somewhat easier; discovering the unreality and untruth of mind is extremely difficult. If one wishes to realize true principle, without meditative concentration there is nothing to be said.

Although one has risen from the seat and is no longer sitting in meditation, the mind still continues the state from within samādhi. This shows that the samādhi of sitting meditation can nourish the active samādhi of walking, standing, sitting, and lying down, allowing the mind to abide in samādhi at all times without distraction. There is a speaker who says that the samādhi of sitting meditation is useless, that people spend most of their time in activity, that sitting meditation lasts only a short while, and that samādhi disappears as soon as one becomes active. The facts demonstrate how absurd this person's claims are and how devoid of factual basis. He himself does not sit in meditation, and opposes everyone else's cultivation of samādhi—he understands nothing about practice.