Shloka 5.58.155
सुन्दरकाण्डे अष्टपञ्चाशः सर्गः — हनुमद्वृत्तान्तकथनम्, सीताभिज्ञान-प्रदानम्, लङ्कादाह-वर्णनम्
ततस्तन्नगरद्वारं वेगेनाप्लुतवानहम्।पुच्छेन च प्रदीप्तेन तां पुरीं साट्टगोपुराम्।।।।दहाम्यहमसंभ्रान्तो युगान्ताग्निरिव प्रजाः।
tatas tan-nagara-dvāraṃ vegenāplutavān aham |
pucchena ca pradīptena tāṃ purīṃ sāṭṭa-gopurām |
dahāmy aham asaṃbhrānto yugāntāgnir iva prajāḥ ||
Then I sprang swiftly to the city-gate; and with my tail blazing, I began to burn that city with its ramparts and great gateways—calm and unconfused, like the end-time fire consuming the world.
"Then I leaped to the entrance gate of the city without being perplexed. With my burning tail I set fire to the boundaries and towering mansions which looked like the world at the end of dissolution.
Dharma here is punitive justice directed at adharma: Hanuman’s burning of Lanka functions as a moral warning and strategic blow, carried out without panic or cruelty for its own sake.
With his tail still aflame, Hanuman escapes control and begins setting fire to Lanka’s structures, moving from the city-gate onward.
Sthairya (steadiness): he remains asaṃbhrānta—clear-minded—while executing a dangerous act.