Canto 3 -
Araṇya-kāṇḍa
Chapter 46: Rāvaṇa Disguises Himself and Approaches Sītā
Text 3.46.4

तामाससादातिबलो भ्रातृभ्यां रहितां वने।
रहितां चन्द्रसूर्याभ्यां सन्ध्यामिव महत्तमः॥

tām āsasādātibalo bhrātṛbhyāṁ rahitāṁ vane
rahitāṁ candra-sūryābhyāṁ sandhyām iva mahat tamaḥ

tām = her; āsasāda = approached; atibalaḥ = the very strong Rāvaṇa; bhrātṛbhyām = [the protection of] the two brothers Rāma and Lakṣmaṇa; rahitām = without; vane = [when she was] in the forest; rahitām = [when it is] without; candra-sūryābhyām = the moon and the sun; sandhyām = [approaching] twilight; iva = like; mahat = intense; tamaḥ = darkness.

Like intense darkness [approaching] twilight [when it is] without the moon and the sun, the very strong Rāvaṇa approached her [when she was] in the forest without [the protection of] the two brothers Rāma and Lakṣmaṇa.