Kural # 71:

அன்பிற்கும் உண்டோ அடைக்குந்தாழ் ஆர்வலர்
புன்கணீர் பூசல் தரும்.

Rough translation:

Can love (towards our dear ones) ever be confined within a safe lock? The tears that automatically well up when one watches the suffering of our loved ones will make the love in our hearts clear to all.

There are so many memorable lines in Tamizh literature and I suppose அன்பிற்கும் உண்டோ அடைக்குந்தாழ் must be added to them. So much meaning and beauty packed into so few words.