In autumn 1849, a slender six-page work was printed in Czernowitz, Bukovina, under the title Tzava’a (Will). Earlier that year, in March, Bukovina became a separate Austrian crown land; today the region straddles the border between Romania and Ukraine.The 1849 pamphlet is rare. The National Library of Israel holds a solitary copy, and there is only one other copy listed in the catalogue of libraries in Israel.In addition to the standard imprint information, the title page announces that the work includes three items; each item is detailed in a different size font. This paratextual feature indicates what someone in the publishing process thought about the relative significance of each of the three items in the pamphlet, and seeks to communicate to readers what is more important, what is of secondary import, and what was inserted as an addendum.In the largest font and listed first – the ethical will of Rabbi Aharon Perlow of Karlin (1736-1772), transcribed from his own handwriting. In a smaller font and listed third – the conduct advice penned by Rabbi Asher Perlow of Stolin (1760-1826), son of Aharon. In between these two items, in a still smaller font – the smallest on the title page – and in a different script: “Also a pleasant zemer [Sabbath hymn] from the holy, famous rabbi, our master Rabbi Aharon, who is mentioned above, who would sing inspired by the holy spirit on the holy Sabbath.” This “pleasant hymn” is none other than the now famous and widely sung “Yah Echsof” – often referred to as “Kah Echsof” in order to avoid saying God’s name in vain. The relative size of the font and the use of what is commonly known as Rashi script suggests that someone involved in the printing process thought that this was merely a supplement to the main contents of the publication.Nowadays you would be hard pressed to find someone who is familiar with Aharon’s ethical will or someone whose daily regimen includes reading Asher’s conduct counsel as per his recommendation, whereas “Yah Echsof” is part of the Shabbat soundscape in many homes and communities.MOST OF the Shabbat zemirot come from the medieval poets. They were composed beginning in the 14th century through the 17th century. Thus, a zemer from 18th-century Poland is unexpected, and its publication in 19th-century Bukovina surprising. To be sure, the hassidic movement would come to be associated with nigunim (songs) – with or without words – sung as part of religious practice. Yet this is the only example of a Shabbat zemer from the hassidic milieu that is widely known.Students of medieval poetry might criticize the composition for its lack of rhyme and meter. Indeed, in certain places the Hebrew phrasing seems to have been clumsily sewn together. Such an assessment misses the depth of the poem and the enormity of Aharon the Great’s achievement.Aharon was clearly in conversation with the hallowed Jewish poetic tradition. Indeed, there are turns of phrase taken from his poetic predecessors. Thus, “Yah Echsof” echoes the other poems sung around the Sabbath table and singers can easily identify words that appear elsewhere in the zemirot canon.The most visible expression of how “Yah Echsof” joins the medieval poetic tradition is the use of acrostics.Medieval poets would often sign their names with acrostics. To illustrate the phenomenon, each stanza of the popular “Dror Yikra” has four lines. The acrostic of the four lines of the first stanza gives four Hebrew letters: dalet, vav, nun, shin, spelling Dunash – a reference to the poet Dunash ben Labrat (920-990), hailed as the founder of Andalusian Hebrew poetry. Dunash’s penchant for acrostics did not end with the first stanza; the same acrostic appears in the four lines of the second, third, and sixth stanzas (but not in the fourth and fifth stanzas). Dunash also wrote “Devai Haser,” a short four-line poem recited in many communities as an introduction to Grace After Meals at a wedding celebration. True to form, the acrostic formed by the four lines gives the poet’s name.Aharon followed the pattern, but instead of signing his own name in the four stanzas of “Yah Echsof,” he signed the poem with the tetragrammaton. Perhaps Aharon was crediting God for the inspiration needed to pen the poem.Notwithstanding, the author did not entirely hide his involvement. An acrostic made from the second word of each of the four stanzas gives the name Aharon, as if the poet was humbly saying that his contribution was secondary to the role of the Almighty in composing the hymn.Aharon’s hidden words did not end there. The acrostic from the third word of each stanza spells “neshama” (soul).Weaving the three acrostics together – God, Aharon, neshama – it is as if the poet is offering an explanation for his work: This divine poem, put down on paper by Aharon, is sourced in the soul and speaks to the soul.The writer, a rabbi in Tzur Hadassah, is on the faculty of the Pardes Institute of Jewish Studies and a postdoctoral fellow with the Galicia project at the University of Haifa.