Pratyahara
pratyāhāraThe fifth limb, usually glossed as withdrawal of the senses: the hinge where practice turns from the body to the mind.
The senses spend all day reaching outward. The fifth limb is the unusual move of letting them settle back:
The drawing in of the organs is by their giving up their own objects and taking the form of the mind-stuff, as it were.
The original Sanskrit
svaviṣayāsaṃprayoge cittasvarūpānukāra ivendriyāṇāṃ pratyāhāraḥ
And the payoff is stated with the Sutras' usual economy:
As a result of this [withdrawal] there is complete mastery of the organs.
The original Sanskrit
tataḥ paramā vaśyatendriyāṇām
If you have ever closed your eyes in class and felt the room grow quiet from the inside, you have brushed against this limb.