Kural - 87

To reckon up the fruit of kindly deeds were all in vain;
Their worth is as the worth of guests you entertain

Explanation
The advantages of benevolence cannot be measured; the measure (of the virtue) of the guests (entertained) is the only measure.

Tamil Transliteration
Inaiththunaith Thenpadhon Rillai Virundhin
Thunaiththunai Velvip Payan.