yathaakaashasthito nityam vaayuhu sarvatrago mahaan |
tathaa sarvaani bhootaani matsthaaneetyupadhaaraya || 6 ||

Just like the mighty wind travels everywhere, established in space, so too, all beings reside in me, understand this.
yathaa : just like
aakaashasthitaha : established in space
nityam : eternally
vaayuhu : wind
sarvatragaha : travels everywhere
mahaan : mighty
tathaa : so do
sarvaani : all
bhootaani : beings
matsthaani : reside in me
iti : in this manner
upadhaaraya : understand this
The key teaching of the chapter is that Ishvara pervades everything, that all beings are sustained by Ishvara but Ishvara is not contained in any of them. To illustrate these statements, Shri Krishna compares Ishvara to space. He says that space enables everything to exist within it, like wind, for example. In the same way, all living and non-living entities dwell in Ishvara.
First, let us understand the nature of space. It is indivisible, which means that even if we try to divide it by building walls, we cannot do so. It does not get affected by what it contains. A flower generates fragrance when fresh and odour when it decays. But both those qualities do not get transferred to space, since space has no qualities. It also pervades everything. Over 99% of an atom is empty space. And it is infinite. No object can ever contain space.
Similarly, Shri Krishna says that Ishvara is infinite, indivisible, pervades everything, and remains unaffected by what he sustains. How does this help us? Knowing that Ishvara is everywhere reduces our sorrow, delusion, fear, likes and dislikes. If everything is Ishvara, and if we also know that we are in Ishvara, there is nothing to fear or like or dislike. That is how we get liberated.
There is a story in the Ishvaavaasya Upanishad. The gods tried to have a race with Ishvara. But wherever they ended up, Ishvara was already there. Another interpretation of this story is that the senses also tried to outrun Ishvara, but could not. It is like trying to race with space. It is a futile effort, because space is all-pervading. So is Ishvara.
Now, just like we see the blue sky with our eyes, we also see things and people on this earth being created and destroyed. We know that the blue colour is an illusion, but do we really understand that creation and dissolution is an illusion as well? This is taken up next.