Hi guys...
here is citation from CE on Arjun-Ashwatthma battle- when they both release the Brahma-astra and they are both urged to withdraw it
"O Arjuna! O Pandava! O Arjuna! In your mind, you have the knowledge of the divine weapon that was instructed to you by Drona. The time to use it has arrived. O descendant of the Bharata lineage! It is needed to save yourself and your brothers. You should release it, since it is capable of countering all weapons." Having been thus addressed by Keshava, Pandava, the destroyer of enemy heroes, swiftly descended from the chariot and grasped his bow and an arrow. The scorcher of enemies spoke words of welfare, addressed to his preceptor's son, then to himself and all his brothers. He bowed to the gods and all his preceptors. Meditating and pronouncing auspicious words, he released that weapon, so as to pacify the other weapon. That weapon was violently released by the wielder of Gandiva. It blazed with great flames, like the fire that arises at the end of a yuga. In a similar way, the weapon released by Drona's son was fierce in its energy. It blazed in great flames, surrounded by a disc of energy. There were many peals of thunder and thousands of meteors fell down. A great fear was generated in all the beings. The firmament was enveloped in that great noise and seemed to be covered in a terrible garland of fire. The entire earth, with its mountains, forests and trees, trembled. That weapon was stationed there, scorching the worlds with its energy.
The two rishis said, "The maharathas who have fallen down earlier were knowledgeable about many weapons. These weapons should never be used against humans. Why have you invoked them?"'
Dhananjaya quickly withdrew his divine arrow. He joined his hands in salutation and spoke to the best of rishis. "This weapon was used by me to pacify the other weapon. Once I withdraw this supreme weapon, all of us will be destroyed. It is certain that Drona's son, the perpetrator of wicked deeds, will consume us with the energy of his weapon. The two of you are like gods. You should think of a means so that we, and all the worlds, are saved." Having spoken these words, Dhananjaya again withdrew his weapon. In an encounter, it is difficult for even the gods to do this. 37 With the exception of Shatakratu himself, no one other than Pandava was capable of withdrawing a supreme weapon, once it had been released in a battle. Once invoked, it was full of Brahma's energy. With the exception of someone with a cleansed soul and someone who was a brahmachari, no one else was capable of withdrawing it. If a person is not a brahmachari, and having released the weapon, wishes to withdraw it, the weapon will sever his head, with that of his descendants. Arjuna had followed the vows of a brahmachari. He had obtained a weapon that was difficult to get. However, he had never invoked it, not even in a time of great calamity. Pandava followed the vows of truth. He was brave and a brahmachari. He was obedient to his superiors. It was because of this that Arjuna was capable of withdrawing that weapon again. Drona's son saw that the two rishis were stationed in front of him. However, in the encounter, he was incapable of again withdrawing that terrible weapon. In the encounter, he was incapable of restraining that supreme weapon. O king! Distressed in his mind, Drona's son addressed Dvaipayana. "I was distressed because I confronted a great calamity. I was scared of saving my life. I released the weapon out of fear. I was scared of Bhimasena. In attempting to kill Dhritarashtra's son, he acted in accordance with adharma. O illustrious one! Bhimasena resorted to falsehood in the battle. O brahmana! Though I have not cleansed my soul, this is the reason I invoked this weapon. I do not have any interest in withdrawing it, even now. Once this celestial weapon has been released by me, it is invincible. O sage! I have invoked it with the energy of the fire and with mantras, To bring an end to the Pandavas'. Therefore, it has been created for the destruction of the Pandaveyas. It will now destroy all the sons of Pandu who are alive. O brahmana! With my senses destroyed by anger, I have committed a wicked deed. Created by me in this encounter, this weapon will slaughter the Parthas."
Debroy, Bibek (2013-12-15). Mahabharata: Volume 8 (p. 54). Penguin Books Ltd. Kindle Edition.