The works of Ādi Śaṅkarācārya

Viṣṇusahasranāmastotram

Verse 398

वनवाससुमुखत्वाद्वा दाशरथी रामः सुमुखः ॥स्वपितुर्वचनं श्रीमानभिषेकात्परं प्रियम् ।मनसा पूर्वमासाद्य वाचा प्रतिगृहीतवान् ॥इमानि तु महारण्ये विहृत्य नव पञ्च च ॥

In plain words

Or: because he turned a glad face toward exile in the forest, Rāma the son of Daśaratha is Sumukha. "That radiant man took his father's word — dearer to him than the crown — into his heart first, and then said yes out loud." "And having roamed nine years and five in the great forest…"

Close to the Sanskrit

Or, from being pleasant-faced with regard to dwelling in the forest, Rāma the son of Daśaratha is Sumukha. "The splendid one, having first received in his mind his own father's word — dearer to him than the consecration — accepted it with his speech." "And having roamed these nine and five in the great forest…"