Tirukkural-On Virtue - The Glory Of Renunciation - Kural 25

1. Aintavitthan attral akalvicumpular komaan
   indirane saalum kari.

The lord India himself is effective witness to the prowess of a sage,
who has really conquered his five senses.

The normal interpretation of the reference to Indra is that the prince of the wide heavens, as manakudavar would say, has trepidations of the heart, whenever a sage effectively controls all his five senses and reaches the heights of penance, lest he should ultimately endanger his own position - and so naturally, he is the witness to the ascetic's prowess. But there are many others including Parimelalagar and V V S Iyer, who think that the reference here, is to the spoliation of Akhalya, for which her sage-husband cursed Indra, in a manner, that he would not lightly forget. I would personally prefer Manakudavar's prosaic interpretation which is more in keeping with Valluvar's general line. This is also one of the rare occasions, when Valluvar specifically refers by name to one of the gods of the Hindu Pantheon.