Canto 3 -
Araṇya-kāṇḍa
Chapter 48: Sītā-devī Condemns Rāvaṇa
Text 3.48.15

स्थापयित्वा प्रियं पुत्रं राज्ञा दशरथेन यः।
मन्दवीर्यः सुतो ज्येष्ठस्ततः प्रस्थापितो ह्ययम्॥

sthāpayitvā priyaṁ putraṁ rājñā daśarathena yaḥ
manda-vīryaḥ suto jyeṣṭhas tataḥ prasthāpito hy ayam

sthāpayitvā = installed on the throne; priyam = his beloved; putram = son; rājñā = King; daśarathena = Daśaratha; yaḥ = who; manda-vīryaḥ = was deficient in heroism; sutaḥ = son; jyeṣṭhaḥ = his eldest; tataḥ = and then; prasthāpitaḥ hi ayam = exiled.

King Daśaratha installed his beloved son on the throne and then exiled his eldest son who was deficient in heroism.

“His beloved son” refers to Bharata.

Rāvaṇa considers Śrī Rāma to be deficient in heroism since He was exiled [to the forest] despite being the eldest son [of King Daśaratha].1

1 Rāvaṇa is being deceptive here. He is actually frightened of Rāma—that is why he chose to kidnap Sītā without facing Śrī Rāmacandra in a duel. So who is actually deficient in heroism?