Agastya was a Vedic Rishi, also known as Saptrishi, a celebrated scholar of Vedas credited with many Hymns.
There are number of miracles and myths associated with Agastya, so his birth too. The Matsya Purana’s account of Agastya’s birth in this way - Sage Narada enquired of Bhagavan Shankara about the origin of Agastya Muni and Vasishta. Lord Shiva explained that once Indra despatched Vayu ( The god or air) and Agni( The fire God) to destroy Danavas ( demons) and having successfully killed thousands of the enemies, ignored some Daityas like Taraka, Kamalaaksha, Paravasu, Kaladamshtra and Virochana as they fled away and concealed in deep Seas. The Danavas who hid themselves kept on tormenting human beings as also Devatas ( the divine beings) eventually. Indra ordered that Vayu and Agni should dry up the Sea water, especially to kill dangerous Danavas like Jambhasura, but the both the Devas argued that in the process of drying up the Seas even in a minor manner there would be serious havoc caused to crores of Jeevas ( living beings)
Hearing this argument, annoyed Indra cursed Vayu and Agni to fall down on Earth from Swarga( heaven) and both the Devas entered into a Jala Kumbha or Water Pitcher as a single body. Meanwhile, Sages Nara and Narayana were in Tapasya ( penance) on Gandhamadana Mountain, and Indra was concerned that they might be a threat to his chair; he despatched a few Apsaras to the Mountain along with Kamadeva ( Lord of Love) but their attempts to tempt the Maharshis failed. As the Apsaras continued to be stationed there, Narayana Rishi created a damsel of exquisite attraction from his thighs and named her Urvasi; he desired that Apsaras should realize that their beauty was nothing compared to whom they could materialize as Urvasi and they could not possibly tempt Nara Narayan Maharshis. Mitra -Varuna happened to see the damsel and could not resist the fall of their combined semen of Mitravaruna which was deposited in the same Jala Kumbha (pitcher) that fell down from the Swarga and thus Agastya was born as Kumbha Sambhava.
It is said that Vashishtha was also reborn from the pitcher so Agastya and Vashishtha are regarded brothers. The story goes back when Vasishtha was visiting King Nimi but king did not properly attend to him and therefore Vashishtha gave a curse to King Nimi to live as Videhaor or be without body, but the King too gave a return curse; both Nimi and Vasishtha approached Lord Brahma who solved the problem by retaining Nimi’s life in his eyes and Vasishtha to be reborn to Mitravaruna since the latter semen fell in the pitcher on seeing Apsara Urvashi.
Over the span of his lifetime, Agastya is given many names, however, the one he is known by, around the time of his birth, is Kumbhayoni, or jar-born. it is widely accepted that he knew a great deal about the Rg Veda, the sciences, and weaponry.
Agastya is celebrated scholar of Vedas, he is mentioned in all the four Vedas, and is a character in the Brahmanas, Aranyakas, Upanishads, epics, and many Puranas.
He is the author of hymns 1.165 to 1.191 of the Rigveda He ran a Vedic school (gurukul), as evidenced by hymn 1.179 of the Rigveda which credits its author to be his wife Lopamudra and his students. He was a respected sage in the Vedic era, as many other hymns of the Rigveda composed by other sages refer to Agastya.
The hymns composed by Agastya are known for verbal play and similes, puzzles and puns, and striking imagery embedded within his spiritual message.he can be found in mandala 1 and 7 both ( Agastya is mentioned in both the oldest and the youngest layers of the Rigveda such as in hymn 33 of mandala 7, which is older than mandala 1. He is also mentioned in other three Vedas and the literature.
From Saints of India - A series on saints of India by Vivek ji