In plain words
This is the oneness that all the sādhakas and all the great ṛṣis of that age went on teaching.
The ornaments are different; the gold is one. The colours of the cattle are different; the milk is one. Living creatures are different; the indweller is one. Castes and customs are different; birth is one. The philosophies are different; God is one. The kinds of flowers are different; the worship is one. Unable to know this, men lose their wits and, for the sake of living, are bound by many sorrows.
For the sake of a livelihood we breed so many kinds of feelings and tear our lives to pieces. One more small example. In the waking state we see so many sights. We go through so many states. But when we go into the state of sleep, all things, everything, we create for ourselves by ourselves. He creates himself. He creates his sorrows and joys too. He creates the whole world. He becomes bound in it. But when he goes into the state of perfect deep sleep, he forgets everything and, in silence, attains a kind of state of samādhi. The one who experienced in the waking state is himself. The one who created in the dream state is himself. The one who attained oneness in the state of deep sleep is himself. The states are three, but the person is one. This is Tat tvam asi. That is, in these three times, in the three states, in the three conditions, the one who experienced is one person. In just the same way, as long as one is in this body, it is understood that this is humanness.
We have recognised humanness, but we do not try to recognise the human qualities. What we must first achieve and understand today is the human qualities. However many positions we hold, however much learning we master, whatever kinds of greatness we gain, what we must remain and what we must achieve is humanness.