In plain words
The Self is never born and never dies. It does not come into being and then pass away. Unborn, always existing, eternal, the ancient one: even when this body is killed, it is not killed. Take this to heart.
Word for word
This Self is ever without birth and death; it does not come into being and pass away. Unborn, ever existent, eternal and ancient, it is not slain even when this body is killed. Understand this.