Monks, in the past a tortoise was searching for food along the bank of a river one evening. On that same evening a jackal was also searching for food along the bank of that same river. When the tortoise saw the jackal in the distance searching for food, it drew its limbs and neck inside its shell and passed the time keeping still and silent.

The jackal had also seen the tortoise in the distance searching for food, so he approached and waited close by, thinking: When this tortoise extends one or another of its limbs or its neck, I will grab it right on the spot, pull it out, and eat it. But because the tortoise did not extend any of its limbs or its neck, the jackal, failing to gain access to it, lost interest in it and departed.

So too, Monks, Māra the Evil One is constantly and continually waiting close by you, thinking, ‘Perhaps I will gain access to him through the eye or through the ear or through the nose or through the tongue or through the body or through the mind.’ Therefore, Monks, reside guarding the doors of The Six Sense Bases. Having seen a form with the eye...Having heard a sound with the ear...Having smelt an odor with the nose...Having tasted a flavor with the tongue...Having touched a physical object with the body…Having recognized a mental object with the mind, do not grasp its signs and features. Since, if you leave the eye sense base unguarded, the ear sense base unguarded, the nose sense base unguarded, the tongue sense base unguarded, the body sense base unguarded, the mind sense base unguarded, evil unwholesome states of craving and displeasure might invade you, practice the way of its restraint, guard the eye sense base, the ear sense base, the nose sense base, the tongue sense base, the body sense base, the mind sense base, undertake the restraint of the eye sense base, the ear sense base, the nose sense base, the tongue sense base, the body sense base, and the mind sense base.

When, Monks, you reside guarding the doors of The Six Sense Bases, Māra the Evil One, failing to gain access to you, will lose interest in you and depart, just as the jackal departed from the tortoise.

Drawing in the mind's thoughts

As a tortoise draws its limbs into its shell,

Independent, not harassing others, fully extinguished.

A Monk would not blame anyone.

(Reference: SN 35.240)

In this Teaching from Gotama Buddha, he shares Teachings to help Practitioners understand that developing a “guard” over The Six Sense Bases is crucial for the development of the mind on The Path to Enlightenment.

A Practitioner needs to deeply understand the problem of the unEnlightened mind which is its mental longing and strong eagerness (craving/desire/attachment/wants/expectations/grasping/holding), craving for sensual pleasures through The Six Sense Bases. Due to the craving/desire/attachment for agreeable and pleasant sensual pleasures, the mind causes itself to be discontent.