Jayapatākā Swami: Aśvattāmā did not know how to withdraw the brahmāstra but he knew how to cast it. And somehow, I did not read anywhere that he can only send the brahmāstra once. It was not proper for him to release the brahmāstra if he did not know how to stop it. And Arjuna knew how to take and how to withdraw. So Kṛṣṇa told him to send his brahmāstra and the two would meet each other, and then Arjuna could withdraw both.
13-March-2021 Śrīdhāma Māyāpur, India