“…In what way, friends, has the Blessed One said that a person is subject to decline? Here,
1. a bhikkhu does not get to hear a teaching he has not heard before,
2. forgets those teachings he has already heard,
3. does not bring to mind those teachings with which he is already familiar, and
4. does not understand what he has not understood.
It is in this way that the Blessed One has said a person is subject to decline.
“And in what way, friends, has the Blessed One said that a person is not subject to decline? Here,
a bhikkhu gets to hear a teaching he has not heard before,
does not forget those teachings he has already heard,
brings to mind those teachings with which he is already familiar,
and understands what he has not understood. It is in this way that the Blessed One has said a person is not subject to decline….
Read the entire translation of Aṅguttara Nikāya 10.55 Parihānasutta: Decline by Bhikkhu Bodhi on SuttaCentral.net. Or read a different translation on SuttaCentral.net. Or listen on SC-Voice.net.