The sixth limb of the seven-part practice is entreating the Buddhas and teachers to turn the wheel of dharma. Turning the Wheel of Dharma is an idiomatic expression for teaching. In the fifth practice, one requests the Buddha, bodhisattvas and masters to live long in the world to benefit the world. In this case, one entreats the enlightened beings to teach the dharma to the beings in the world.
This practice is important because the best and most lasting benefit the enlightened beings can bring to the world is by showing the true path to happiness and enlightenment, which they have themselves trodden. By teaching the path and instilling wisdom and light of knowledge, they dispel ignorance, the main cause of existential problems. Thus, one must request the Buddha and masters to turn the wheel of dharma, i.e. teach the dharma.
The metaphor of turning the wheel is used to describe the act of teaching because when the enlightened masters teach, the inner wheel of understanding and realization is turned in the minds of the disciples. Discerning wisdom and various noble qualities, like the axle and spokes of the wheel, are triggered into motion and new distance is covered on the spiritual path. Thus, by turning the external wheel of dharma through teaching, the inner wheel of spiritual experience is turned. This leads a person to the state of enlightenment, which is the ultimate state of peace and happiness according to Buddhism.