Tirukkural 312: Not Doing Evil

It is the determination of the spotless not to do evil, even in return, to those who have cherished enmity and done them evil.

Image of Satguru Sivaya Subramuniyaswami
A satguru is needed because the mind is so cunning and the ego is a self-perpetuating mechanism. It is he who inspires, assists, guides and impels the shishya toward the Self of himself.
—Gurudeva