Canto 3 -
Araṇya-kāṇḍa
Chapter 20: Rāma Kills the Fourteen Rākṣasas
Text 3.20.11-12

तस्य तद्वचनं श्रुत्वा राक्षसास्ते चतुर्दश।
ऊचुर्वाचं सुसङ्क्रुद्धा ब्रह्मघ्नाः शूलपाणयः॥

संरक्तनयना घोरा रामं संरक्तलोचनम्।
परुषं मधुराभाषं दृष्ट्वा दृष्टपराक्रमम्॥

tasya tad vacanaṁ śrutvā rākṣasās te catur-daśa
ūcur vācaṁ susaṅkruddhā brahmaghnāḥ śūla-pāṇayaḥ

saṁrakta-nayanā ghorā rāmaṁ saṁrakta-locanam
paruṣaṁ madhurābhāṣaṁ dṛṣṭvā dṛṣṭa-parākramam

tasya = of His; tat = those; vacanam = words; śrutvā = upon hearing; rākṣasāḥ = rākṣasas; te = those; catuḥ-daśa = the fourteen; ūcuḥ = they and spoke; vācam = words; susaṅkruddhāḥ = became extremely angry; brahmaghnāḥ = killers of brāhmaṇas; śūla-pāṇayaḥ = had spears in their hands; saṁrakta-nayanāḥ = and their eyes became red [in fury]; ghorāḥ = fierce; rāmam = at Rāma; saṁrakta-locanam = whose eyes were [naturally] reddish; paruṣam = [the following] harsh; madhura-ābhāṣam = whose speech was sweet; dṛṣṭvā = they looked; dṛṣṭa-parākramam = and whose prowess they had [already] witnessed.

The fourteen rākṣasas became extremely angry upon hearing those words of His. Those fierce killers of brāhmaṇas had spears in their hands and their eyes became red [in fury].1 They looked at Rāma, whose eyes were [naturally] reddish, whose speech was sweet and whose prowess they had [already] witnessed, and spoke [the following] harsh words.2

1 Technical note: saṁrakta-nayanāḥ rāma-vacana-śravaṇa-janita-kopa-hetukāruṇya-viśiṣṭa-netravantaḥ. 

2 As it will be clear from Rāmāyaṇa 3.39.10-13, Rāma had already killed two rākṣasas who had accompanied Mārīca in Daṇḍakāraṇya. So the rākṣasas had already witnessed Rāma’s prowess to some extent.