Kural - 997

Though sharp their wit as file, as blocks they must remain,
Whose souls are void of 'courtesy humane'

Explanation
He who is destitute of (true) human qualities (only) resembles a tree, though he may possess the sharpness of a file.

Tamil Transliteration
Arampolum Koormaiya Renum Marampolvar
Makkatpanpu Illaa Thavar.