6. SishyanAy ninRathu - sishyanirukkumiruppu nAttAr aRiyAmaiyAlE aththai aRivikkaikAka.
If one wonders why Sriman Narayana who is the first among acharyas took on the role of a sishya, the answer is, since the jIvas in this world were not aware of the true nature of a disciple, He donned the role of one.
Sri PBA Swami's Sarartha Deepikai:
There may arise a question that why should He simply not have released the Thirumanthra as an acharya; why did He also have to take on the role of a sishya. The answer is that because the souls in this world did not know the nature of a sishya He took the role of a sishya and made known the nature of one. A further question might arise that did He have to actually become a sishya; could He not have simply advised the nature of a sishya to everyone. Had He done that it is possible that jIvas might think that He is announcing the Thirumanthra just to gather fame for Himself. By His becoming a sishya the jIvas would begin to wish that they too become sishyas to acharyas.
The nature of a sishya is this: one who is faithful to Sastras, one whose mind wishes to follow the dharmas detailed in them, one who has the mental strength to follow them, one who practices Bhakti to Sriman Narayana, one who does not have pride in him for having the above, one whose love for his acharya cannot be measured by others, one who has no equal in his faith to his acharya, one who is restless in his service to his acharya. Also, one who considers himself and everything he has, as belonging to his acharya is a sishya.
Nyasa Vimsathi explains the nature of a sishya thus: a sishya is one who has the knowledge of what to give up and what to keep as a means to his higher goal, one who based on this knowledge surrenders to his elders, one whose every day acts are based on this knowledge, one who seeks to understand the higher truth, one who is in the service of his acharya, one without ego, one who bows with his entire body, one who looks forward to listen and learn, one who has control of his mind and body, one who has no hatred toward anyone or anything, one who stays in his acharya's abode, one who has faith in the Sastras, one who has gratitude, such a person should be accepted and taught as a disciple.
Sriman Narayana became a sishya to show the above nature of a sishya.