Jarā: Aging
Jarā is the body's decline over the years. Eighty years, today: Barzillai offers the number to David as his whole answer, and it is enough of one. He has crossed the Jordan to see the king home and now measures himself honestly, treating his age as a fact about a body rather than a grievance to be soothed.
Indriya: The sense faculties
Indriya are the powers of eye, ear, tongue, and the rest. Taste has gone flat and the singers have grown faint, so the king's table and the court musicians would be wasted on him. These are borrowed tools that thin with use, and he has been honest enough to check his own before accepting an invitation built entirely on their working.
Anicca: Impermanence
Anicca is the passing quality of all conditioned things. "Any more" carries the weight: he once tasted, he once heard the singing men and singing women, and those powers left the way daylight leaves a room. Nothing was stolen from him. What he had was on loan the whole time, and eighty years is long enough to watch the loan come due.
Devadūta: The divine messenger
Devadūta names the aged, the sick, and the dying as messengers who wake the rest of us. An old man before a king, listing what he can no longer taste or hear, is that message delivered in person. David is riding back to his throne at the height of his restoration, and the friend who fed him in the wilderness is the one telling him what waits at the end of the road.
Maraṇasati: Mindfulness of death
Maraṇasati is keeping one's own death in plain view. Barzillai turns down a room in Jerusalem because he has already settled where he wants to lie, near his father and mother in his own city. Having a rough sense of how far he has left tells him exactly what to do with the little that remains.
Santuṭṭhi: Contentment
Santuṭṭhi is being satisfied with what one already has. "Why should your servant be a burden" is the question of a man who can no longer enjoy the reward and so declines to consume it. Wealthy enough to have supplied an army, he asks only for a short walk home, and he sends young Chimham to take the seat at the king's table in his place.