Saṃvega: The shock that wakes you
Saṃvega is the jolt of alarm that turns a person toward practice. Josiah tore his clothes when the recovered book was read aloud, and the whole "therefore" of Huldah's reply hangs on that tearing. A man who feels the floor give way beneath him has already begun to move, and the trembling itself is what earns him the answer his messengers carry back.
Kamma: Deed and its fruit
Kamma is action ripening into result. The evil coming on this place was sown over generations of kings before him, and a harvest comes up in its own season, never when the farmer would prefer. Josiah's own tenderness ripens on its own schedule too, which is why his portion differs from his city's though he lives inside its walls.
Anicca: Impermanence
Anicca is the passing nature of everything put together out of parts. "This place" means the temple and the city, stone and gate and hill, and stone is exactly what will not hold. The scroll just found in the house of the Lord will outlast the walls that sheltered it, since nothing built stays standing.
Maraṇassati: Keeping death in view
Maraṇassati is holding one's own death steadily in mind. Being gathered to your fathers is spoken here as kindness, and it is still the plain sentence: you will die, soon enough that the siege will miss you. Comfort arrives in the shape of a grave, the way an old traveler is told his bags are packed and the cart is waiting at the door.
Santi: Peace as cooling
Santi names the quiet that comes when the burning stops. Gathered to your grave in peace cannot mean untroubled politics, since Josiah takes an arrow at Megiddo; the peace is that his heart has stopped fighting what he heard read. A fire that has burned all the way down leaves warm ash and no flame, and that is what is promised to a king who humbled himself before the words.