He ceased: and Raghu’s son obeyed: Upon his string the hero laid An arrow, like a snake that hissed. Whose fiery flight had never missed: The arrow Saint Agastya gave And blessed the chieftain’s life to save That dart the Eternal Father made The Monarch of the Gods to aid; By Brahmá’s self on him bestowed When forth to fight Lord Indra rode.

In plain words: Rama, the son of the Raghu family, follows the advice and fits a hissing, never-missing arrow to his bow. It was given to him by the sage Agastya, and Brahma had first made it to help Indra, king of the gods.