http://www.apamnapat.com/articles/Mahabharata015.html
Here is link which shows that krishna did not ask arjun to abduct as it is
He first say to arjun if u can make subhadra fall in love with u then u can abduct her
Here brief story about arjun and subhadra love
Arjun has already fallen in love with subhadra after listening about her from friend gada ( who belongs to vrishni , a part of yadav clan)
He want to share his feelings to subhadra but before that he went to exile after breaking rule
Then after arjun came as disguise in dwarka so that no one could know him
But shree krishna was omnipresent and he recognizes arjun and even very well know why Arjun has come
Then arjun share that he is in love with subhadra. Lord krishna told that he has no problem Arjun marrying subhadra
Lord krishna says if u can make subhadra fall in love with u. U can abduct her . So krishna first make plans to meet subhadra with arjun
Here balram. Ask arjun to come in palace but arjun refuse because he was not allowed to enter palace until exile over so Arjun stayed in garden
Here subhadra meet Arjun. Till then she was not aware he was arjun
And subhadra was also fallen in love with arjun after listening from gada and krishna but she never saw arjun
So she ask arjun (who was in disguise) about Arjun
After having some talk subhadra come to know that he is Arjun and both fell in love with each other
And when both fell in love with each other then krishna ask arjun to abduct subhadra