Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 1: Contents of the Rāmāyaṇa Summarized
Text 1.1.61

सुग्रीवः शङ्कितश्चासीन्नित्यं वीर्येण राघवे॥

sugrīvaḥ śaṅkitaś cāsīn nityaṁ vīryeṇa rāghave

sugrīvaḥ = Sugrīva; śaṅkitaḥ ca = doubtful; āsīt = was; nityam = always; vīryeṇa = of the strength; rāghave = of the descendant of Raghu.

Sugrīva was always doubtful of the strength of the descendant of Raghu.

From the time Sugrīva saw Rāma until He pierced the Sāla trees, Sugrīva was repeatedly doubtful of Rāma’s strength, that is, he doubted whether Rāma was a hero equal to Vālī or not.