Thirukkural 793

குணமும் குடிமையும் குற்றமும் குன்றா இனனும் அறிந்தியாக்க நட்பு.

Gunamum kudimaiyum kutramum kunra inanum arindhiyakka natpu.

Friendship requires you to discern virtue and fault, family standing and failing, in your friend as if they were as unchanging as a mountain.