Krishna noticed Arjuna’s interest and told him that Subhadra was his sister and that he would talk to his father if Arjuna was willing to marry her.
Later, Krishna explained that there were several accepted forms of marriage in the Kshatriya dharma, and one of them was Rakshasa form of marriage, in which the bride can be abducted after defeating the opposition.
He advised Arjuna to marry Subhadra according to the Rakshasa custom because he could not guarantee that she would choose Arjuna.
Before taking any action, Arjuna sent a messenger to Yudhishthira and to Vasudeva, Subhadra’s father, seeking their approval before abducting her.
Only after receiving their approval did Arjuna proceed.
Arjuna, along with Krishna, learnt that Subhadra would visit Mount Raivataka, and together they devised a plan.
Soon, Arjuna mounted his golden chariot and carried his weapons. In order to avoid suspicion, he set out as though he were going to hunt.