Magen Avot is a genre of piyyut designed to be inserted into the blessing Berakha Aḥat Me‘en Sheva‘ in the Jewish liturgy for Friday evening, right before the words "Magen avot bidvaro" ("He shielded the patriarchs with His word"), from which the name of the genre is taken.
The first known author to write a poem in this genre was Joseph Kimhi, who was born in Muslim Spain, but spent his later life in Narbonne, Provence.
[2] Kimhi wrote two piyyutim to embellish this prayer: the first one, “Yom Shabbat Zakhor” (יום שבת זכור), is intended to be recited before the beginning of the standard liturgical paragraph “Magen Avot”, and every line ends in the syllable "-hu", to rhyme with the end of the first sentence of “Magen Avot” (ha-’el ha-qadosh she-’en kamohu);[3] the second one, “Yom Shabbat Shamor”, is intended to be recited before the second line of the standard paragraph ("He gives rest to His people on His holy Sabbath day, for He desired them, to give rest to them"), and every line ends in the syllables "-lehem", to rhyme with the end of that second line in the standard paragraph, (ki vam raẓa le-haniaḥ lahem).
In the late 13th century, Samuel Devlin of Erfurt wrote a Magen Avot poem “Shipperam Ram Be-ruḥo” (שפרם רם ברוחו), following the style of “Yom Shabbat Zakhor”, and intended to be inserted in the same place in the liturgy.
The twentieth-century scholar Ezra Fleischer collected, from Ashkenazic manuscripts, no fewer than eighteen such poems, by various poets, for occasions throughout the year, such as: a Sabbath that falls on Rosh Chodesh, or Hanukkah, or Rosh Hashana, or Shabbat Naḥamu; and lifecycle events, such as a Sabbath on which a wedding or circumcision is being celebrated in the community.