One might conclude that the word “sword” in Buddhist scriptures appeared for the first time in a Song of the Brethren (Theragāta 1, 757). There we find asattha (n. adj.) [a = negating particle + sattha] “absence of a sword or knife”, which indicates a characteristic of the monk: he is non-violent.
The word sword, however, is more often given als asi, a vedic expression, i.e. belonging to the Sanskrit lore that shaped Hinduism.
It is therefore remarkable that Buddha-ghosa (“Buddha-voice”), a fifth-century native of Bodhgaya in northern India, who migrated to Sri Lanka where he penned his large commentary on the Pali canon under the title Visuddhi-magga, mixed Sanskrit-elements with his newly acquired command of the Pali language. We find another example in Cittā’s gātā.
In his Visuddhimagga Buddhaghosa speaks of ñānāsi which by most translators is translated as “the sword of knowledge“. The paragraph in one of the translation runs as follows (Vism.II, ch, xii):
6. And these enemies (ari), these defilements, are destroyed (hata) by the path. / Because the enemies are thus destroyed he is thus accomplished (arahanta)./ The enemies (ari) that were deployed / [i.e.] greed and the rest, have been destroyed (hata) / by his, the Helper’s, wisdom’s sword (ñānāsi), / So he is “accomplished” (arahanta), all agree on that.
We might say that here, in ñānāsi, we do not encounter a combination of subject and object. Therefore we might translate it as “the sword (āsi) which is knowledge (ñānā).” Ñānā in Buddhist philosophical thinking is generally given a somewhat subordinate place in comparison with paññā, and especially with bodhi. Bodhi (or buddh) is invariably given as “wisdom”. When at the end of his First Exposition of his dharma (or dhamma) Buddha exclaims: “Aññā Kondañña“, he says: “Kondañña knows!”, not “Kondañña has attained to supreme wisdom [buddhi] or insight [pañña]”.
As Buddhaghosa’s family belonged to the upper stratum of Indian society he must have had discussions with brahmin priests who cited the famous Bhagavad Gīta verse (ch.4, 42):
“Therefore, with the sword of knowledge, cut asunder the doubts that have arisen in your heart. O scion of Bharat (India), establish yourself in karm[a] yog[a]. Arise, stand up, and take action!” (“Karma yoga” being the religious cultivation through action.)
Certainly this verse speaks of knowledge that cuts through doubts (or ignorance in other translations) just as a sword cuts through matter. Why later on Arjuna, the main character of the Gīta yet saw the need for using the sword in cutting through matter, Buddhaghosa may not have gotten a satisfactory answer to. Nevertheless, this use of the word sword in connection with knowledge (or wisdom in other translations) must have stuck in his mind, and once in Sri Lanka he jotted the ñānāsi down at the appropriate place, in the passage that describes how the arahan (the enlightened who has almost attained to Buddhahood) cut through the defilements of the mind, so liberating himself. In doing so Buddhaghosa led the reader back to the original meaning of the word: the monk, or arahan (arhat) does not use a sword, and certainly not in the literal sense. His “sword” is his knowledge/wisdom.
Many centuries later when the 13th century Vietnamese zenmonk Tue Trung apparently spoke in riddles when answering questions by his disciples he too refers to the sword, but hardly in combination with knowledge or wisdom.
He says (Les Propos de l’Éveillé Tue Trung, Paris 2015, p.63/64)
Kiém truóc Long Tuyén hiêu
A marvelous sword called Dragon’s Source (Une épée merveilleuse appelée Source de Dragons)
Kiém xung xuát hap cáu khói phuc,
The sword is drawn out of its sheat to re-establish peace (L’épée sort du fourreau pour rétablir la paix),
The Vietnamese word for sword is kiẽm.
Where did Tue Trung got this concept of sword from? Was he inspired by Buddhaghosa? That is highly unlikely since his first utterance “A marvellous sword called Dragon’s Source” rather belongs to East-Asian religio-philosophical iconography, and not to the Indian lore.
In the Chinese language one of the translations for sword is jiàn. Is the Vietnamese kiẽm a degeneration of the Chinese jiàn? This seems to be the case. Where did Buddhist China the concept of “the sword called Dragon’s Source” get from? From the Serindian Buddhist canon as it had been carried over the border at Dunhuang? Not so sure.
In Tibetan Buddhist parlance, taught and brought back from the earliest university of Nalanda — a Buddhist(ic) interpretation that did not come to the fore before the 6th/7th century — we find: “flaming ‘sword of wisdom’ “, given as “shes rab ral gri“. Gri meaning “sword”. Tibetan translators even came up with a Sanskrit(ic) source: chūrikā as in prajñā-chūrikā: “knife of wisdom” which they eventually altered into ‘sword of wisdom’, in line with Buddhaghosa’s ñānāsi but a tad different because ‘we’re no theravādin, we’re sarvastivādin if not vajra-yānin. Hence we don’t employ the dictionary of the theravādin.’
It’s therefore not the Tibetan prajñā-chūrikā (wisdom-sword) that Tue Trung had come across. Was he inspired by monks that accompanied Mongolian invadors into Vietnam and Korea? The Mongolian word for sword is ildü (or ildy(n) in the first English-Mongolian dictionary by the hand of Ferdinand D Lessing). No, ildü and kiẽm are in no way comparable.
The only conclusion is therefore that Vietnam obtained the concept of flaming sword out of China, and that China used this concept in the most literal form possible — as all concepts that China uses are to be understood in the literal sense of the word.
The sequence is therefore as follows:
In the earliest period of Buddhism the monk did not carry a sword, i.e. he was by nature and praxis non-violent;
In Buddhaghosa’s 5th century wisdom had become a symbol that, as a sword, cut through mental defilements;
In the next Chinese and Mongolian period of Buddhism one employed a literal flaming sword in ceremonies that were designed to establish the opinion that (evil and/or) ignorance had to be forcefully destroyed — stamp it out!;
In the Vietnamese 13th century the king-monk used the sword wisely (in his opinion) to literally re-establish peace, not to cut through ignorance of defilements.