This (Maharaja Pariksit is miraculously saved in the womb of his mother) was caused by Drauni (Asvatthama), Acarya Drona's son, who killed the five sons of Draupadi while they were asleep, for which he was punished by Arjuna

Expressions researched:
"This was caused by Drauṇi (Aśvatthāmā), Ācārya Droṇa's son, who killed the five sons of Draupadī while they were asleep, for which he was punished by Arjuna"

Srimad-Bhagavatam

SB Canto 1

This was caused by Drauṇi (Aśvatthāmā), Ācārya Droṇa's son, who killed the five sons of Draupadī while they were asleep, for which he was punished by Arjuna.

SB 1.7.1, Translation and Purport

Ṛṣi Śaunaka asked: O Sūta, the great and transcendentally powerful Vyāsadeva heard everything from Śrī Nārada Muni. So after Nārada's departure, what did Vyāsadeva do?

In this chapter the clue for describing Śrīmad-Bhāgavatam is picked up as Mahārāja Parīkṣit is miraculously saved in the womb of his mother. This was caused by Drauṇi (Aśvatthāmā), Ācārya Droṇa's son, who killed the five sons of Draupadī while they were asleep, for which he was punished by Arjuna. Before commencing the great epic Śrīmad-Bhāgavatam, Śrī Vyāsadeva realized the whole truth by trance in devotion.