Kural - 786

Not the face's smile of welcome shows the friend sincere,
But the heart's rejoicing gladness when the friend is near

Explanation
The love that dwells (merely in the smiles of the face is not friendship; (but) that which dwells deep in the smiles of the heart is true friendship.

Tamil Transliteration
Mukanaka Natpadhu Natpandru Nenjaththu
Akanaka Natpadhu Natpu.