Zend or Zand (Middle Persian: 𐭦𐭭𐭣) is a Zoroastrian technical term for exegetical glosses, paraphrases, commentaries and translations of the Avesta’s texts. The term zand is a contraction of the Avestan language word zanti (𐬰𐬀𐬌𐬥𐬙𐬌, meaning “interpretation”, or “as understood”).

Zand glosses and commentaries exist in several languages, including in the Avestan language itself. These Avestan language exegeses sometimes accompany the native text being commented upon, but are more often elsewhere in the canon. An example of exegesis in the Avestan language itself includes Yasna 19–21, which is a set of three Younger Avestan commentaries upon the three Gathic Avestan ‘high prayers’ of Yasna 27. Zand also appears to have in the same way as existed in a variety of Middle Iranian languages, but of these Middle Iranian commentaries, the Middle Persian zand is the solitary one to survive fully, and is for this excuse regarded as ‘the’ zand.

With the notable exception of the Yashts, almost anything surviving Avestan texts have their Middle Persian zand, which in some manuscripts appear alongside (or interleaved with) the text mammal glossed. The practice of including non-Avestan commentaries next door to the Avestan texts led to two different misinterpretations in western scholarship of the term zand; these misunderstandings are described below. These glosses and commentaries were not meant for use as theological texts by themselves but for religious suggestion of the (by then) non-Avestan-speaking public. In contrast, the Avestan language texts remained sacrosanct and continued to be recited in the Avestan language, which was considered a sacred language. The Middle Persian zand can be subdivided into two subgroups, those of the permanent Avestan texts, and those of the loose Avestan texts.

A consistent exegetical procedure is evident in manuscripts in which the indigenous Avestan and its zand coexist. The priestly scholars first translated the Avestan as literally as possible. In a second step, the priests then translated the Avestan idiomatically. In the pure step, the idiomatic translation was complemented subsequent to explanations and commentaries, often of significant length, and occasionally bearing in mind different authorities inborn cited.

Several important works in Middle Persian contain selections from the zand of Avestan texts, also of Avestan texts which have in the past been lost. Through comparison of selections from directionless texts and from long-lasting texts, it has been realistic to distinguish in the middle of the translations of Avestan works and the commentaries on them, and suitably to some degree reconstruct the content of some of the directionless texts. Among those texts is the Bundahishn, which has Zand-Agahih (“Knowledge from the Zand“) as its subtitle and is crucial to the concurrence of Zoroastrian cosmogony and eschatology. Another text, the Wizidagiha, “Selections (from the Zand)”, by the 9th century priest Zadspram, is a key text for treaty Sassanid-era Zoroastrian orthodoxy. The Denkard, a 9th or 10th century text, includes extensive summaries and quotations of zand texts.