Kural - 103

Kindness shown by those who weigh not what the return may be:
When you ponder right its merit, 'Tis vaster than the sea

Explanation
If we weigh the excellence of a benefit which is conferred without weighing the return, it is larger than the sea.

Tamil Transliteration
Payandhookkaar Seydha Udhavi Nayandhookkin
Nanmai Katalin Peridhu.