Kural - 101

Assistance given by those who ne'er received our aid,
Is debt by gift of heaven and earth but poorly paid

Explanation
(The gift of) heaven and earth is not an equivalent for a benefit which is conferred where none had been received.

Tamil Transliteration
Seyyaamal Seydha Udhavikku Vaiyakamum
Vaanakamum Aatral Aridhu.