Question
What is the Pashupatastra? Did Arjuna use it in the Kurukshetra war?
Answer
1) What is Pashupatastra ?
Pashupatastra is the personal favourite weapon of Lord Shiva.
Just like weapons of Lord Brahma,
= Brahmastra, Brahmashirastra, etc...
weapons of Lord Vishnu,
= Narayanastra, Vaishnavastra, etc..
similarly weapons of Lord Shiva,
= Pashupatastra, Maheswarastra, Raudrastra, etc...
Literally,
Pasupatastra = Weapon of Pasupati
So, there can be two category. One is special Pasupatastra (which Arjuna received) which is very powerful. One General Category can fall as denoting weapon of Pasupati (ie. It may be any weapons containing power of Pasupati).
General category Pasupatastra is described one time in Mahabharat. It was used by Drona and Arjuna simply destroyed it. It was not that special Pasupatastra received by Arjuna as Arjuna cuts it simply. Also, Lord Shiva had told 'No man know it..' while giving Pasupatastra to Arjuna. So, it is not that special Pasupatastra. It is just used to denote weapon presided by some subtle power of Pasupati.
When Drona failed to gain any ascendency over the son of Pandu, the son of Bharadwaja, that warrior acquainted with the course of all weapons, invoked into existence the Aindra, the Pasupata, the Tvashtra, the Vayavya, and the Yamya weapons. As soon as those weapons, issued from Drona's bow, Dhananjaya destroyed them quickly. [Drona Parva chapter 188]
However generally if we call Pashupatastra then the special weapon (which Arjuna had received) is understood.
Lord Shiva himself describes here what Pashupatastra is:
Bhava replied, 'O powerful one. I will give to thee that favourite weapon of mine called the Pasupata. O son of Pandu, thou art capable of holding, hurling, and withdrawing it. Neither the chief himself of the gods, nor Yama, nor the king of the Yakshas, nor Varuna, nor Vayu, knoweth it. How could men know anything of it? But, O son of Pritha, this weapon should not be hurled without adequate cause; for if hurled at any foe of little might it may destroy the whole universe. In the three worlds with all their mobile and immobile creatures, there is none who is incapable of being slain by this weapon. And it may be hurled by the mind, by the eye, by words, and by the bow.'" [VanaParva Chapter 60]
2)Why did Lord Shiva get it in first place?
It is personal weapon of Pasupati. So it is always with him.
Bhava replied, 'O powerful one. I will give to thee that favourite weapon of mine called the Pasupata. O son of Pandu, thou art capable of holding, hurling, and withdrawing it. Neither the chief himself of the gods, nor Yama, nor the king of the Yakshas, nor Varuna, nor Vayu, knoweth it. How could men know anything of it? [VanaParva Chapter 60]
Lord Shiva had united Pasupatastra with Shaft used in the Tripura Dahana incident:
Then Sarva, having stringed his bow and aimed that shaft with which he had united the Pasupata weapon, waited thinking of the triple city. And O king, as Rudra thus stood, holding his bow, the three cities during that time became united. When the three cities, losing their separate characters became united, tumultuous became the joy of the high- souled gods. Then all the gods, the Siddhas, and the great Rishis, uttered the word Jaya, adoring Maheshwara. [Karna Parva Chapter 34]
3) Was it the all-knowing Krishna who urged Arjuna to acquire this astra?
Arjuna had received Pasupatastra two times from Lord Shiva. At first time by the words of Indra, Arjuna starts penance for Lord Shiva:
Thus addressed, the slayer of Vritra, worshipped of the worlds, consoling him with gentle words, spare unto the son of Pandu, saying, 'When thou art able to behold the three-eyed trident-bearing Siva, the lord of all creatures, it is then, O child, that I will give thee all the celestial weapons. Therefore, strive thou to obtain the sight of the highest of the gods; for it is only after thou hast seen him. O son of Kunti, that thou will obtain all thy wishes.' Having spoken thus unto Phalguna, Sakra disappeared then and there, and Arjuna, devoting himself to asceticism, remained at that spot." [VanaParva chapter 37]
But as long time had passed Arjuna forgots the knowledge to invoke Pasupatastra during Kurukshetra war. Thus before the day of Jayadratha Vadh Lord Krishna by Yogic path took him to Kailash to receive Pasupatastra again.
Through his grace thou shalt obtain that rich possession.' Hearing these words of Krishna, Dhananjaya, having touched water, sat on the earth with concentrated mind and thought of the god Bhava. After he had thus sat with rapt mind at that hour called Brahma of auspicious indications, Arjuna saw himself journeying through the sky with Kesava. [Drona Parva Chapter 80]
Then both of them gratified Lord Shiva and Arjuna received Pasupatastra one more time.
And the god also granted him the terrible Pasupata weapon and the accomplishment of his vow. Then having thus once more obtained the Pasupata weapon from the supreme god, the invincible Arjuna, with hair standing on end, regarded his business to be already achieved. Then Arjuna and Krishna filled with joy, paid their adorations unto the great god by bowing their heads. And permitted by Bhava both Arjuna and Kesava, those two heroes, almost immediately came back to their own camp, filled with transports of delight. [Drona Parva Chapter 80]
4)Did Arjuna really use it in the Kurukshetra war? If he didn't, why did he get it from Lord Shiva?
Pashupatastra was never used in Kurukshetra war. There is popular misconception that Arjuna had used it to slay Jayadratha. It is not true.
Arrow which killed Jayadratha was like this:
Sorely afflicting those mighty car-warriors of thy army thus, the son of Pandu took up a terrible arrow of fiery splendour. Looking like the thunderbolt of Indra, and inspired with divine mantras, that formidable arrow was capable of bearing any strain. And it had been always worshipped with incense and garlands of flowers. Duly inspiring it (by mantras) with the force of the thunderbolt, that descendant, of Kuru, viz., the mighty-armed Arjuna, fixed it on Gandiva. [Jayadratha Vadh Parva]
Then why Did Lord Krishna took him to Kailash to receive Pasupatastra before the day of Jayadratha Vadha?
It is because just knowledge of invoking Pasupatastra is sufficient to make one victorious and powerful. It works subtly.
And then that hero, of eyes like lotus leaves, and possessed of great energy, said these words for the benefit of Pandu's son who had resolved upon the slaughter of the ruler of the Sindhus, 'O Partha, there is an indestructible, supreme weapon of the name of Pasupata. With it the god Maheswara slew in battle all the Daityas! If thou rememberest it now, thou shalt then be able to slay Jayadratha tomorrow. If it is unknown to thee (now), adore within thy heart the god having the bull for his mark. Thinking of that god in thy mind, remember him, O Dhananjaya! [Drona Parva Chapter 80]
Furthermore, Pasupatastra is not a weapon which is to be hurled to mortals. It was to be used only in extreme emergency.
Then the god Tryamvaka said unto me, 'I will give. O Pandava, my own weapon Raudra shall attend upon thee.' Thereupon Mahadeva, well-pleased, granted to me the mighty weapon, Pasupata. And, having granted that eternal weapon, he also said unto me, This must never be hurled at mortals. If discharged at any person of small energy, it would consume the universe. Shouldst thou (at any time) be hard pressed, thou mayst discharge it. And when all thy weapons have been completely baffled, thou mayst hurl it.' [Vana Parva chapter 166]
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