In 4:4 of Gita, Arjuna asks an interesting question to Krishna.
Arjuna is inquisitive as to how Krishna had instructed the science of Yoga(union) to the Sun God who thereafter passed this knowledge to Manu.
Arjuna wondered how is it possible for Krishna to have taught the Sun God and Manu had died long time ago. How the heck did Krishna exist then and now.
A genuine doubt, isn’t it?
To that Krishna’s answer was that anyone who is situated in wisdom,like himself and who had slained Maya for good would remember all his births.
And, what about the rest?
They go round and round and remain in this cycle of rebirths till they are ready and willing to fight Maya, the Goddess of Illusion 🙂
Bhagavad Gita Chapter 4, Shlok 5
śhrī bhagavān uvācha
Bahūni me vyatītāni janmāni tava chārjuna
Tānyahaṁ veda sarvāṇi na tvaṁ vettha parantapa//
The Supreme Lord said: Both you and I have had many births, O Arjun. You have forgotten them, while I remember them all, O Parantapa.