Wikipedia
The Nālaṭiyār is a Tamil poetic work of didactic nature belonging to the Patiṉeṇkīḻkaṇakku anthology of Tamil literature. This belongs to the post Sangam period corresponding to between 100 – 500 CE. Nālaṭiyār contains 400 poems, each containing four lines. Every poem deals with morals and ethics, extolling righteous behaviour.
There is an old Tamil proverb praising the Nālaṭiyār that says "Nālaṭiyār and the Tirukkuṛaḷ are very good in expressing human thoughts just as the twigs of the banyan and the acacia trees are good in maintaining the teeth."
ஆலும் வேலும் பல்லுக்குறுதி; நாலும் இரண்டும் சொல்லுக்குறுதி.
(Aalum vaelum pallukkuruthi; naalum irandum sollukkuruthi)
Literal translation: "Banyan and acacia maintain oral health; Four and Two maintain moral health."
(Here "Four" and "Two" refer to the quatrains and couplets of Nālaṭiyār and Tirukkuṛaḷ, respectively.)