Three decades of work, some 50,000 rhyming couplets completed around 1010 CE: Ferdowsi's Shahnameh retells the mythical and legendary history of Iran from the creation of the world to the Arab-Muslim conquest of the Sasanian Empire, in Persian strikingly free of Arabic loanwords. Written when Arabic dominated scholarship and the court across the former Iranian world, the poem is widely credited with helping preserve the Persian language and a distinct Iranian identity within Islam. It became the supreme subject of Persian miniature painting and has been recited and sung ever since.
Ferdowsi wrote in Persian at a time when Arabic dominated religion and much of scholarship and rule, even as a new Persian was already returning to the page. The Islamic conquest had swept away the old Iranian empire three centuries before, and across the conquered lands the language of the conquerors was becoming the language of poetry, science, and the court. Into that world he poured roughly three decades and fifty thousand couplets in a Persian with strikingly little Arabic, retelling the deep past of Iran from the first king to the last. He is said to have boasted, in lines that may not be exactly his, that he had built a monument no rain or wind could wear down and had given the Persians new life through this Persian. Whatever the exact words, a single poem is widely thought to have helped a language survive.