Arjuna uvaacha:
aparam bhavato janma param janma vivasvataha |
kathametadvijaaniyaam tvamaadau proktavaaniti || 4 ||

Arjuna said:
Your birth is in the present, and the sun’s birth was in the past. How should I understand that you had taught this (yoga) in the beginning?

aparam : in the present
bhavatah : you
janma : birth
param : in the past
janma : birth
vivasvataha : the sun
katham : how should
etat : this
vijaaniyaam : understand
tvam : you
aadau : in the beginning
proktavaan : had taught
iti : this

Having heard that Shri Krishna taught karmayoga to the sun, Arjuna had a doubt. How could Shri Krishna have revealed this knowledge to the sun? The sun came first before even the earth came into existence. But Shri Krishna was only a little older than Arjuna, so how does one reconcile this fact?

Therefore, Arjuna requested Shri Krishna to clarify this point. Even the way he asked this question is very beautiful. He could easily have said “I don’t believe you, how is this possible”. Instead, he very humbly says “my mind cannot understand this point, please help me understand it”. There is no accusation or finger pointing of any sort here. It is asked with sincerity.

This question enables Shri Krishna to reveal his true identity to Arjuna in the next shloka.

Footnotes
1. Arjuna has referred to Shri Krishna as bhavataha (respected you, or “aap” in hindi) and tvam (friendly you or “tum” in hindi), further highlighting the reverence and friendliness towards Shri Krishna.