The epic of al-Barraq Ibn Rawhan seems to have originated by the beginning of the 18th century,* and it was widely circulated in the 19th century. Thus far I have tracked down seven sources of the epic, three publications and four manuscripts, which are identified below. It is one of several tales narrated by a certain Dhu'ayb Ibn Nafi' which have sometimes been appended to copies of al-Qurashi's Jamharat Ash'ar al-'Arab.
The story is set in pre-Islamic Arabia and adjacent lands and tells the tale of a young and brave warrior, al-Barraq Ibn Rawhan, who is in love with his first cousin, Layla Bint Lukayz, whom he hopes to marry. Layla is renowned for her beauty, and an Arab king makes a marriage proposal to her father. Much to al-Barraq's chagrin, Layla's father agrees to the engagement. When Layla is sent as part of a convoy to the Arab king, she is kidnapped en route by a half-Arab half-Persian middleman who plans to sell her to a Persian king. Whilst in captivity, Layla utters a poem beginning "If only al-Barraq could see," in which she describes the torture and suffering she endures and calls upon her kinsmen to rescue her. Layla's poem is overheard by a sympathetic servant who conveys it to al-Barraq through a series of messengers. When al-Barraq hears Layla's words, he rallies his people to war. Under al-Barraq's fearless leadership, the Arab armies defeat the Persians and Layla is rescued. Al-Barraq and Layla wed, and it is discovered that she is a virgin--she has successfully warded off sexual violation during her captivity--hence she is known as Layla "the Chaste."
Interestingly, some versions of the epic identify the hero al-Barraq as a Christian.
*Note that Aḥmad ʿAṭiyya's edition of the epic, which is based on two manuscripts in Cairo, attributes it to Umar b. Shabba who died in the 3rd/9th century. However, due to the relatively late provenance of the one of the two manuscripts which is dated--it was copied in 1719--and due to the fact that none of the other sources of the epic attribute it to him, I seriously doubt that the attribution is correct.
Three published versions:
Anonymous, ‘Riwāyat al-Barrāq bin Rawḥān,’ Ḥadīqat al-akhbār 1.39-1.48 (2 October 1858-4 December 1858).
Iskandar Abkāriyūs, ‘Ḥarb al-Barrāq,’ Tazyīn Nihāyat al-Arab fī Akhbār al-ˁArab (Beirut, 1867), 211-300.
Aḥmad ʿAṭiyya (ed.), Kitāb al-Jamhara fī Ayyām al-ʿArab li-l-ḥāfiẓ ʿUmar b. Shabba al-Baṣrī al-mutawaffī sanat 262 hijrī (Ismailiyya: Maktabat al-Imām al-Bukharī, 2015), 69-183.
Ahlwardt 9747, Berlin, copied in 1854, 77v-141v.
Arabe 5833, Paris (copied in 1797), 107v-131.
Ms. Or. Oct. 1383, Berlin, copied in early 1824, 87-147.
Or. 2676, Leiden, undated, 155v-231.
5984 Adab, Dar al-Kutub, Cairo, copied in 1927, 2-119. A copy of 1194 Adab, below.
Two further manuscripts (from theʿAṭiyya edition-not yet directly consulted):
1194 Adab, Dar al-Kutub, Cairo, copied in 1719.
6375 Adab, Dar al-Kutub, Cairo.