Nahj al-balāgha (Arabic: نَهْج ٱلْبَلَاغَة, lit. 'the path of eloquence') is the best-known collection of sermons, letters, and sayings attributed to Ali ibn Abi Talib (d. 661), the fourth Rashidun caliph (r. 656–661), the first Shia imam, and the cousin and son-in-law of the Islamic prophet Muhammad. The compilation of the book is often credited to Sharif al-Radi (d. 1015), a prominent Shia scholar. Known for its moral aphorisms and eloquent content, Nahj al-balagha is widely studied in the Islamic world and has considerably influenced the Arabic literature and rhetoric. In view of its sometimes sensitive content, the authenticity of the book has long been a subject of polemic debates, though recent academic research suggests that most of its contents can indeed be attributed to Ali by tracking the texts in sources that predate al-Radi.