In plain words
There is a reason for this. One day, while Subhadrā was with child, Arjuna went on telling her about the lotus array. Subhadrā kept answering ‘hm’ to what he was telling her, but Abhimanyu, in her womb, heard it all. Just then Kṛṣṇa came there: ‘Arjuna! Do you think Subhadrā is listening to all you are saying? No, no. The child in her womb is listening. So speak no more about the lotus array,’ He said. By then he had finished telling how to enter the lotus array. That is why Abhimanyu was able to get into the lotus array. But not knowing the way to come out, he was caught by the Kauravas and lost his life. So we must not turn a deaf ear to the words our parents have spoken. What the elders have said we must hear with our ears, ponder in our minds, put into practice and digest. In this way we must supply the essence of what we have heard to every limb of the body. “Revere your mother as God, revere your father as God”: this is the authority of the Veda. So we must never disregard our parents' words. Whatever the matter, whatever the situation, we must bow our heads to their command.
Kṛṣṇa and Arjuna came back home from the battlefield. But when Abhimanyu did not come out to meet him the moment he arrived, Arjuna grew anxious. ‘The moment he learns that I am coming, he comes running and folds me in his arms. Why has that dear son of mine not come today?’: so he kept fretting in every way. Learning that Abhimanyu had entered the lotus array and lost his life at the hands of the Kauravas, Arjuna sank into grief. Then Kṛṣṇa, consoling Arjuna: ‘Arjuna! Through the wicked schemes of the Kauravas you have all suffered many hardships. Your son has died now through nothing but the deceit they practised. What has happened has happened. Give no room to weakness,’ He said. Arjuna grew very angry. ‘Kṛṣṇa! Could You not have told me beforehand that my son would die? You too have deceived me. All this has happened because of You alone,’ he reproached Him. Kṛṣṇa did not take offence at Arjuna's words. Kṛṣṇa was ever scattering smiles. That was His nature.
A few months later Uttarā, Abhimanyu's wife, gave birth. But the son born to her was dead. Aśvatthāmā had loosed a weapon charged with Śabdabrahman and killed the child while it was still in her womb. The Pāṇḍavas were crushed. All of them sat in one room, their faces fallen. Even before that, Aśvatthāmā had killed the Upapāṇḍavas, the sons of Draupadī. Abhimanyu, Subhadrā's son, had been trapped in the lotus array and had lost his life. Now even in the son born to Abhimanyu there was no life. There was no one left now who could keep up the line of the Pāṇḍavas. Thinking that Kṛṣṇa alone was the cause of all this, they all blamed Him. Just then Kṛṣṇa came there smiling: “Pāṇḍavas! Haste is not good. Keep calm,” He said, and sat down right in their midst. He commanded Draupadī to bring the child. Draupadī laid the dead child in a small tray and brought it there. Then Kṛṣṇa: ‘Ah! Look at that nose, look at those ears, look at that mouth. All of it is Abhimanyu's likeness!’ So He went on describing the child. The Pāṇḍavas grew angry that He should praise a dead infant so much. Kṛṣṇa took the child into His hands and patted it on the bottom and on the belly. The child gave a sharp cry and wept. Because Kṛṣṇa tested him and gave him life, the boy was named ‘Parīkṣit’. No one can pass and go up to the higher classes without an examination.