Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 1: Contents of the Rāmāyaṇa Summarized
Text 1.1.62

राघवप्रत्ययार्थं तु दुन्दुभेः कायमुत्तमम्।
दर्शयामास सुग्रीवो महापर्वतसन्निभम्॥

rāghava-pratyayārthaṁ tu dundubheḥ kāyam uttamam
darśayām āsa sugrīvo mahā-parvata-sannibham

rāghava-pratyayārtham tu = to make Rāma understand [Vālī’s strength]; dundubheḥ = Dundubhi’s; kāyam = body; uttamam = gigantic; darśayām āsa = showed Him; sugrīvaḥ = Sugrīva; mahā-parvata-sannibham = that resembled a great mountain.

To make Rāma understand [Vālī’s strength], Sugrīva showed Him Dundubhi’s gigantic body that resembled a great mountain.

Sugrīva was not just doubtful. He wanted to understand Rāma’s strength and so showed Him something. He wanted to be convinced of Rāma’s strength. Dundubhi was an asura who had been killed by Vālī. Uttamam indicates that Dundubhi’s body that was just bones now was not slackened and so it resembled a tall mountain. Vālī had kicked Dundubhi with his foot and sent it flying across.