Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 1: Contents of the Rāmāyaṇa Summarized
Text 1.1.58

सुग्रीवश्चापि तत्सर्वं श्रुत्वा रामस्य वानरः।
चकार सख्यं रामेण प्रीतश्चैवाग्निसाक्षिकम्॥

sugrīvaś cāpi tat sarvaṁ śrutvā rāmasya vānaraḥ
cakāra sakhyaṁ rāmeṇa prītaś caivāgni-sākṣikam

sugrīvaḥ ca api = Sugrīva; tat sarvam = all of that; śrutvā = hearing; rāmasya = from Rāma; vānaraḥ = the monkey; cakāra = established; sakhyam = friendship; rāmeṇa = with Rāma; prītaḥ = became happy; ca eva = and; agni-sākṣikam = keeping fire as a witness [to their bond of friendship].

Hearing all of that from Rāma, the monkey Sugrīva became happy and established friendship with Rāma, keeping fire as a witness [to their bond of friendship].

Sugrīva heard all about Rāma and became happy thinking, “Rāma has a need and so do I. He can fulfill my need.”

The friendship was among two persons dissimilar [to each other]: one was Rāma and another was a monkey. This shows Rāma’s extremely good character. He was friendly to Guha who was a lower human being, indicating His good character. He was respectful to Śabarī [who was not only of a low community among human beings, but also] a woman, indicating His good character to a greater degree. [Now, He is establishing a bond of friendship] with Sugrīva, an animal, indicating His good character to the greatest degree.