। ॥ ८१५ ॥
In plain words
Meditation on That is meant to run unbroken — one continuous flow of the mind, like oil poured in a single unbroken thread. And for the whole of that time, keep up the hearing: always, and with real effort.
Close to the Sanskrit
Meditation on That is held to be by an unbroken mental flow, like a stream of oil; for that much time, hearing is always to be done with effort.