Karna’s tutelage under Guru Parashurama and his getting curse by his guru were mentioned, as far as I could locate, in 2 places in Mahabharata.
A. On the 17th day of the war - Karna Parva
अवात्सं वै ब्राह्मणच्छद्मनाहं; रामे पुरा दिव्यमस्त्रं चिकीर्षुः ।
तत्रापि मे देवराजेन विघ्नो; हितार्थिना फल्गुनस्यैव शल्य ॥
कृतोऽवभेदेन ममोरुमेत्य; प्रविश्य कीटस्य तनुं विरूपाम् ।
गुरोर्भयाच्चापि न चेलिवानहं; तच्चावबुद्धो ददृशे स विप्रः ॥
पृष्टश्चाहं तमवोचं महर्षिं; सूतोऽहमस्मीति स मां शशाप ।
सूतोपधावाप्तमिदं त्वयास्त्रं; न कर्मकाले प्रतिभास्यति त्वाम् ॥
अन्यत्र यस्मात्तव मृत्युकाला;दब्राह्मणे ब्रह्म न हि ध्रुवं स्यात् ।
तदद्य पर्याप्तमतीव शस्त्र;मस्मिन्सङ्ग्रामे तुमुले तात भीमे ॥
I once lived with Rama disguised as a brahmana, seeking divine weapons. During that time, Shalya, Indra, wanting to help Phalguna, created an obstruction.
It took the form of a terrible worm and burrowed into my thigh. As my teacher slept with his head resting upon my lap, the worm pierced my thigh. A pool of thick blood flowed from my body because of it, but I didn't move, fearing to disturb my teacher's sleep.
When the brahmana awoke and saw what had happened, he witnessed my patience and said to me, 'You are no brahmana! Tell me truly who you are.' Then, Shalya, I told him the truth, that I was a Suta. Hearing this, the great ascetic, filled with rage, cursed me, saying, 'Because of your deception in obtaining this weapon, Suta, it will fail you in your hour of need, at the moment of your death. Brahman cannot reside in one who is not a brahmana."
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B. In the 3rd chapter of Shanti Parva
कर्णस्य बाहुवीर्येण प्रश्रयेण दमेन च ।
तुतोष भृगुशार्दूलो गुरुशुश्रूषया तथा ॥
तस्मै स विधिवत्कृत्स्नं ब्रह्मास्त्रं सनिवर्तनम् ।
प्रोवाचाखिलमव्यग्रं तपस्वी सुतपस्विने ॥
'That tiger from Bhrigu's lineage, Rama, was well-pleased with Karna's arm strength, his devotion, his self-discipline, and his service to his teacher. Practicing ascetic penances, Rama joyfully taught, with proper rites, his ascetic disciple the secrets of the Brahma weapon and the incantations for retracting it.'
यस्मान्मिथ्योपचरितो अस्त्रलोभादिह त्वया ।
तस्मादेतद्धि ते मूढ ब्रह्मास्त्रं प्रतिभास्यति ॥
अन्यत्र वधकालात्ते सदृशेन समेयुषः ।
O foolish Karna! You have lied to me in your greed for weapons (despite not being a Brahmin, you pretended to be one and learned knowledge). Therefore, in times of crisis, you will forget this Brahmastra. When your time of death is near and you are fighting a warrior as mighty as you, this Brahmastra will be of no use to you, nor will you know.
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As far as I understood, Karna’s tutelage under Guru Parashurama and his getting curse by his guru were interpolated stories The following issues are to be considered for understanding as to what actually transpired.
Interpolated stories incorporated just to project Karna as a tragic hero
The following interpolated stories were incorporated in the Mahabharata about Karna.
i) Karna as the son of Kunti, born out of wedlock, and Indra deprived Karna of his natural armour, in order to save his son Arjuna.
This issue was already mentioned in another post, stating that Karna was the biological son of Radha and Atiratha, but not that of Kunti and Surya. Thus, the question of Indra depriving Karna of his natural armour does not arise.
ii) Indra had pierced Karna’s thigh, when guru Parashurama was sleeping with his head on Karna’s lap
Karna had only 1 curse of Brahmana that his wheel of the chariot will remain struck, for killing his cow.
- Karna mentioning about his Vijaya bow, Bhargavastra, along with his curses from Brahmana and Guru Parashurama only on the 17th day of the war gives rise to doubts, as to why these issues were not presented before Bhishma and Drona, when they were alive and who are also disciples of Guru Parashurama?
- Brahmastra will not be useful in the hour of need to Karna. It indicates that it will be useful in other times.
- Then, why did not Karna use Vijaya bow, Brahmastra in (a) Gosha Yatra against Gandharvas, (b) against Abhimanyu on the 13th day of war, (c) against Bhima on 14th day of the war, when Bhima defeated Karna multiple times, (d) against Arjuna on 14th day of the war, when Arjuna defeated him, before proceeding towards Jayadratha?
- Further, it was also stated that just before Arjuna beheading Karna, Karna discharged Brahmastra against Arjuna and Arjuna countered it. How is it possible, when according to Guru Parashurama’s curse, he cannot use it in the need of the hour?
