Saṃvega: The shock that wakes a person up
Saṃvega is the jolt that turns someone toward practice. Hearing alone did this work: no army had yet crossed the border, and already the shaking had started on the prophet's own doorstep. That tremor is worth more than a calm ignorance, since it is the first honest response to what is coming, the way a doctor's plain word can reorder a life in an afternoon.
Kāyānupassanā: Watching the body
This is attention placed on the body from the inside. Trembling limbs, quivering lips, bones giving way: the dread reports itself in muscle and breath long before any argument with God about justice resumes. Staying with the shaking as shaking is the practice, and the body holds underfoot like solid ground while everything else is rumor.
Maraṇasati: Keeping death in mind
Maraṇasati is holding one's own death in view on purpose. Rottenness entering the bones is death arriving early, felt in the marrow while the man is still upright and still speaking. Monks sat among corpses to learn this without waiting for an invasion; someone who has already felt his bones go soft has less left to lose when the horsemen finally come up over the hills.
Anicca: Impermanence
Anicca is the mark of change on everything made. A people coming up to invade is exactly this: a city that was safe is about to stop being safe, and no arrangement of walls and treaties holds. Reading the Chaldean advance as one more turn of change, rather than a personal ambush by heaven, drains some of the panic without denying an ounce of the loss, much as weather is faced instead of argued with.
Khanti: Patient endurance
Khanti is the strength to bear what cannot yet be changed. Waiting quietly for the day of trouble is hard labor: the trembling continues, the invasion stays on its way, and still he keeps his place rather than fleeing or wringing an answer out of God. This is the farmer's patience, who cannot pull the season forward and so stands with the field through the storm, which is why the quiet here sits on top of terror instead of replacing it.