Matsyapurana 144.101

144.101

yugeṣvetāni hīyante trayaḥ pādāḥ krameṇa tu
ityeṣa pratisaṃdhirvaḥ kīrtitastu mayā dvijāḥ //

O Dvijas! I have told you about the sandhis which pertain to the yugas only. One Manvantara is seventy one times these four yugas. The four yugas make one cycle, and each yuga in every cycle is of one and the same nature. So the fourteen Manvantaras revolve.—101-104

When the Satyayuga comes in its people are procreated by those who remained at the end of Kaliyuga The good and perfect persons that remained unnoticed amongst the Brâhmanas Ksatriyas, Vaisyas and Sûdras they and the Saptarṣis now give instructions in dharma to the new people In that way the doctrines of the Risis based on Śrutis and Smṛitis are propagated They promulgated Varnâsrama Dharma and other rituals on the lines of Śrutis and Smṛitis The Saptarṣis hold the dharma of the Śrutis and Smritis For promulgating dharma the Saptarṣis are ever ready in every Satyayuga These Risis are now existing for the period of one Manvantara As the roots of plants and trees vigorously germinate after being consumed by fire, similarly, there is a growth in the generation of people at the commencement of the Satya age. In this way, generations of the ages go on for ever The ideas appear and disappear. Comforts, life power, beauty, dharma, Artha and Kāma lose onefourth their quantity in every Yuga—92-100