Kural - 801

Familiarity is friendship's silent pact,
That puts restraint on no familiar act

Explanation
Imtimate friendship is that which cannot in the least be injured by (things done through the) right (of longstanding intimacy).

Tamil Transliteration
Pazhaimai Enappatuvadhu Yaadhenin Yaadhum
Kizhamaiyaik Keezhndhitaa Natpu.