Nagarjuna says in Essence of Dependent Relationship,
From three develop two;
From two develop seven;
From seven develop three.
Hence, from the three delusions – ignorance, craving and grasping, two actions develop: compositional actions and existence. From these two actions, seven fruits of suffering develop: consciousness, name and form, six sources, contact, feeling, birth, and ageing and death. From these seven, again, the three delusions develop: ignorance, craving and grasping. In this manner, the chain interlocks and samsara is established in perpetual motion.