This question came up in the Online 10-day Retreat Nov 3, 2020, guided by Delson Armstrong. Day 1 was part of a daily 30-minute discussion on the suttas, the Dhamma talk and reflections.
Slightly edited to improve readability
Extremely important, because as you start to still the body, you are already working on the lower jhanas, with the stilling and tranquilizing of the bodily Formations. Not only is your breathing, if you notice it, becoming less apparent and starts to become – not necessarily shallow, but just feeble, and it doesn’t really affect the body. Secondly, it starts to lower the heart rate, blood pressure, starts to bring things into equilibrium for the body. That is why you start to lose certain sensations of the body. You’re tranquilizing and stilling the physical Formations when you do that.
As soon as you move, or as soon as there is contact made with the physical body, you have Perception of that physical body. This then creates further Formations, in experiencing the physical body again. Whether it’s through your own movement, or through Contact with the body.
It’s very important to keep the body still in the sitting practice. In the practice of walking, you are obviously moving the body and you’re still working with physical Formations, because you are intending the walking while you are doing it. But I would say, it’s more important to sit. I see the walking as an exercise for the mind, to be able to bring and generate the Loving-kindness out into the world. And as a way to cultivate it, in whatever the way is that you might be doing it.
But in the sitting practice, it’s crucial to sit still. Number one because as you progress through the jhanas and as your body becomes still, you are tranquilizing the bodily Formations. And up to the level of the fourth jhana, Contact with the body becomes almost imperceptible. And then come the Formless Realms, as they call it, the dimensions of Infinite Space, Infinite Consciousness, Nothingness and Neither-Perception-nor-non-Perception.
In the first and second jhana, you are dealing with the verbalizations. If you see in the first jhana you verbalize, or you have an intention of sending out Loving-kindness to yourself or your spiritual friend; that’s the verbal Formation that is being at play. Then, as you get into the second jhana, or when you start from the second jhana onwards, you don’t use the verbalizations and the intention is quickly let go of. There is only the awareness of the Feeling. At this point you have already, for the most part, stilled the verbal Formations.
That’s not to say that you will not have verbalizations that arise in the way of thoughts, certain stray thoughts that might come and go, that sound like verbalizations. That also can be dealt with from the fourth jhana onwards, that’s no problem. But these verbalizations are coming from the intention that is conditioned by the verbal Formations. By silencing the mind, stopping the verbalizations, you are stopping the intention and thereby you’re also stopping the verbal Formations that condition that intention.
As you get higher into the fourth level, you’re stilling the bodily Formations. As you get deeper and deeper, especially into Nothingness and Neither-Perception-nor-non-Perception, you’ll start to have stray thoughts, images and things like that, that might be disconnected. Especially in Neither-Perception-nor-non-Perception. When you have them, those are really now working with the mental Formations, which are the Feeling and Perception. As you start to let go of those and 6R that, then you have basically stilled all the Formations, and activated and balanced the Factors (of Awakening) and you enter into Cessation of Perception and Feeling.
That’s basically a long way of saying that it’s extremely important to still the body when you’re meditating 🙂