The Bhagavad Gita compares a sage of Yoga to what animal?

• a tortoise in its shell

Is Muni, is the Sage, the true Recluse!
He who to none and nowhere overbound
By ties of flesh, takes evil things and good
Neither desponding nor exulting, such
Bears wisdom's plainest mark! He who shall draw
As the wise tortoise draws its four feet safe