Kural - 808

In strength of friendship rare of friend's disgrace who will not hear,
The day his friend offends will day of grace to him appear

Explanation
To those who understand that by which they should not listen to (tales about) the faults of their friends, that is a (profitable) day on which the latter may commit a fault.

Tamil Transliteration
Kelizhukkam Kelaak Kezhudhakaimai Vallaarkku
Naalizhukkam Nattaar Seyin.