Valmiki Ramayana · Sundara Kanda · Sarga 4
प्रविश्य नगरीं लङ्कां कपिराजहितंकरः।।5.4.2।। चक्रेऽथ पादं सव्यं च शत्रूणां स तु मूर्धनि।
praviśya nagarīṃ laṅkāṃ kapirājahitaṃkaraḥ cakre'tha pādaṃ savyaṃ ca śatrūṇāṃ sa tu mūrdhani|
Hanuman, a devotee of the king of monkeys entered the city of Lanka placing his left foot first on the forehead of the city and proceeded (by tradition one enters the enemy's dwelling by placing the left foot first to cause defeat of the enemy).
— M.N. Dutt (1891)
Commentary
Hanuman enters with his left foot first — a detail that matters. In Indian tradition the left foot is considered auspicious for entry. Even in stealth, Hanuman maintains reverence. He is not a thief in the night but a messenger on a sacred errand.
वामप्रवेश