The first sloka-(प्रथम श्लोका)

The Killing of Krouncha Heron
Vālmīki was going to the river Ganges for his daily ablutions. A disciple by the name Bharadvāja was carrying his clothes. On the way, they came across the Tamasa Stream. Looking at the stream, Vālmīki said to his disciple, "Look, how clear is this water, like the mind of a good man! I will bathe here today." When he was looking for a suitable place to step into the stream, he saw a Crane (bird) couple mating. Vālmīki felt very pleased on seeing the happy birds. Suddenly, hit by an arrow; the male bird died on the spot. Filled by sorrow its mate screamed in agony and died of shock. Vālmīki 's heart melted at this pitiful sight. He looked around to find out who had shot the bird. He saw a hunter with a bow and arrows, nearby. Vālmīki became very angry. His lips opened and he uttered the following words:
"मां निषाद प्रतिष्ठां त्वमगमः शाश्वतीः समाः। यत्क्रौंचमिथुनादेकम् अवधीः काममोहितम्॥"
mā niṣāda pratiṣṭhāṁ tvamagamaḥ saswatih samāḥ
yat krauñcamithunādekam avadhīḥ kāmamohitam
You will find no rest for the long years of Eternity
For you killed a bird in love and unsuspecting
Emerging spontaneously from his rage and grief, this was the first śloka in Sanskrit literature. Later Vālmīki Muni composed the entire Rāmāyaṇa with the blessings of Lord Brahmā in the same meter that issued forth from him as the śloka. Thus this śloka is revered as the "first śloka" in Hindu literature. Vālmīki Muni is revered as the first poet, or Ādi Kavi, and the Rāmāyaṇa, the first Kāvya.
His first disciples to whom he taught the Rāmāyaṇa were Kuśa and Lava, the sons of Śrī Rāma.