Is what a friend wanted to know.
As the Pandavas were climbing up the cold Himalayas to submit themselves to death, they had no weapons with them. They had discarded them. Except Arjuna, who had his divine bow, Gandiva, with him. It is not that he wanted it for his or his brother’s protection in the mountains. It is just that he was deeply attached to it. It is not clear from the narrative whether for keeping the bow he had the permission of Yudhisthira or the approval of his brothers.
But whatever is given is taken away, sometimes early, sometimes late. Krishna had given him a fraction of his kala (attribute) and he withdrew it when he was giving up his mortal form. Told by Sahadeva not to do so, Arjuna would not touch him, despite Krishna’s pleading. So he requested Arjuna to extend Gandiva towards him so that he could have a feel of his dearest sakha (friend) at least indirectly; isn’t a touch of someone dearest soothing when one is in pain? That’s the way Arjuna thought and as he held out the bow, the avatara touched it and with that he withdrew his attribute. At once Arjuna became like any other mortal. The youngest Pandava, who knew everything, knew that the avatara would not return from the world incomplete, leaving a bit of him behind. So he had asked his brother not to touch him, no matter how heart-rending his pleading. But there are limits to human intelligence; the purna avatara (complete manifestation of all attributes) was not bound by any.
It was fire god Agni’s turn now. At the time of the burning of the forest of Khandava, he had given this divine bow to Arjuna. Now he manifested and told Arjuna that he had come to take back Gandiva. Arjuna refused right away. It was not merely a weapon for him; he loved and respected it so profoundly that he had taken an oath that he would not forgive any disrespect to either Krishna or Gandiva – just them; no Kunti, no Yudhisthira, no Draupadi – and would kill the offender. Everyone knew of his oath. Thus once he was going to kill Yudhisthira when he insulted Gandiva. Krishna intervened and saved the sanctity of Arjuna’s oath and Yudhisthira’s life both. That story that does not concern us here.
Agni pleaded with him but Arjuna was reluctant. This was when Yudhisthira intervened. He sharply told Arjuna that if he was so attached to his bow he should return to Hastinapura and assist King Parikshita in the protection of the kingdom. Arjuna got the message and gave his bow to the god. It must have dawned on him that clinging to worldly things, including the divine ones given by gods, was actually clinging to life. Attachment to life negated the last jajna that he was performing along with his brothers and Draupadi in the sacred Himalayas.
Then Agni said something that was intended as much for him as for the listeners of the great narrative, sitting in front of Sarala more than five centuries ago, and also his listeners and readers since then: Arjuna should not feel disappointed. In future times Mahabharata would be re-enacted again and again and Arjuna would return again and again, and at that time he would give back Gandiva to him. The poet does not tell us what these words meant to Arjuna – if at all he registered them – but he informs and warns those who were listening to him and those who would in future about the human conditions, about the inevitabilities.
Sarala does not tell us whether there would be Krishna in the future enactments of Mahabharata. He knew that there was no point trying to figure out what Narayana would do. He knew that He is beyond the comprehension of anyone – man or god. He knew that Agni knew it too.