In plain words
Well, these five went to Bhīṣmācārya. Dharmaja bowed to Bhīṣma: ‘Grandsire! We lost our father when we were still small. From our childhood you brought us up, raised us, taught us every vidyā and reared us as a father would. With you, who are like a father to us, we have set about making war. Kindly grant us your leave,’ he prayed. Then Bhīṣma recognised Dharmaja's feeling for dharma, and tears welled up in his eyes. ‘My son! Even in a situation like this, not overstepping the path of dharma in the least, you have come to receive my leave! You are following the path of dharma, so may you win victory on every side,’ he blessed him. At once Dharmaja came to his guru Droṇācārya: ‘Swami! You are our guru; we are your disciples. Ācārya! Aśvatthāmā is your own son. We too are just like sons to you, because you taught us learning and good sense, loved us like your own sons and brought us up. But by force of time, karma and circumstance, today we have had to make war on you. So you must give us your leave,’ he prayed to Droṇācārya. The heart of Droṇācārya, the guru, melted. At once he embraced Dharmaja and said, ‘Dharmo rakṣati rakṣitaḥ.’
So, even in a terrible situation where no one knew in which minute, in which moment, whose life would go, the Pāṇḍavas kept to dharma alone. Holding that following this dharma was itself Kṛṣṇa's aim, they showed forth, in every work they did, the goal of establishing Dharma. To say that such Pāṇḍavas took the path of adharma, that they spoke Asatya to Droṇācārya, has no basis whatever.
Students! In the Purāṇas you read, or in the Bhārata, the Bhāgavata and the Rāmāyaṇa you read, doubts of some kinds may strike you, some fancies may come. You must not be thrown by the very fancies in you and set about taking only the faults in them. You must recognise the truth that in the deeds of God, or in the stories of God, there is no deed without a reason. There are many inner meanings. But because you take only the meaning of the words, the meaning of the sentence and the outer meaning, and cast aside the true meaning, the right meaning does not come to you.