To support the order of natural evolution, Lord Vishnu follows his incarnation as a fish (matsya) with that as kurma, a giant tortoise. This incarnation is set in the midst of the Samudra Manthan, the churning of the great ocean, a mythological narrative where the good and the evil work collectively to gain riches and ambrosia but only the virtuous gain immortality at the end as per Vishnu’s plan. During this churning, the great tortoise places the mandara parvata (mountain) on its back so that the mountain can be supported as a stirring rod. Besides making the gods, who possess goodness, immortal, Vishnu strengthens dharma at the conclusion of the incarnation by blessing the worlds with Ayurveda, the science of life.
In a spiritual sense, the tortoise signifies the perfection of yoga. In the Bhagavad Gita, God-incarnate Krishna compares the tortoise’s ability to retract its limbs and head into the shell to the withdrawal of a yogi’s senses from their objects (2: 58), which is a feature of the stable mind. This makes the tortoise a symbol of introspection or renunciation from the external environment and links the Lord’s kurma avatar to the sponsorship of yogic practices in the universe. Vedic astrology (Jyotish) supports the same by linking the kurma avatar to the planet Saturn (see Brihat Parashara Hora Shastra), which is the astrological significator for discipline, renunciation, and austerity.
The gain of numerous riches, perfect health for all, and immortality for the gods as a consequence of the Lord’s second incarnation shows how one can achieve these objectives in life through perfection in yoga. However, the real aim of yoga remains the Lord himself who bestows everything upon the individual souls while letting them participate in his divine plays.