The Heart Sutra dates from the 4th century and, like the Diamond Sutra, is a condensation of Buddhist wisdom literature. Its main teaching is that all reality is empty, i.e. without any permanent, abiding nature. The realization of this fluidity and impermanence of reality is none other than nirvana, enlightenment. Chanting the Heart Sutra is a common practice in many Japanese Zen and Korean Son traditions.