prajopadravam ālakṣya loka-vyatikaraṁ ca tam mataṁ ca vāsudevasya sañjahārārjuno dvayam
Translation
Arjuna, thus seeing the disturbance of the people in general also imminent destruction of the planets, at once retracted both the Brahmastra weapons because Lord Sri Krishna expressed His opinion in that way.
Purport
The theory that the modern atomic bomb explosions can annihilate the world is a childish imagination. First of all the atomic energy is not so powerful as to destroy the world. And the second thing is that ultimately it rests on the supreme will of the Supreme Lord because without His will or sanction nothing can be built up or destroyed. It is foolish also to think that natural laws are ultimately powerful. The material nature's law works under the direction of the Lord as it is confirmed in the Bhagwat Geeta. The Lord says there that natural laws work under His supervision. The world can be destroyed only by the will of the Lord and not by the whims of tiny politicians. Lord Sri Krishna desired that the weapons released by both Drouni and Arjuna may be withdrawn and it was carried by Arjuna at once. Similarly there are many agents of the All powerful Lord and by His will only one can execute what He desires and what to speak of Himself.