SHIR HA-YIḤUD (Heb. שִׁיר הַיִּחוּד; "Hymn of Unity"), a lengthy medieval liturgical poem divided into seven parts, one for each day of the week, praising God, extolling His uniqueness, and emphasizing the smallness of His creatures. Poetic beauty and sublimity of religious thought have placed the poem among the foremost liturgical compositions. Each line is divided into rhymed couplets, with four beats in each couplet. From the fourth line on, each verse throughout the remainder of the poem contains 16 syllables. The first three lines serve as an introduction, a free translation of which reads:
I will sing to my God as long as I live,
The God who has sustained me all through my life,
To this day Thou hast taken me by the hand,
Life and loving kindness hast Thou given me.
Blessed be the Lord, blessed be His glorious name,
For His wondrous kindness shown to His servant.
(trans. P. Birnbaum, High Holiday Prayer Book (1951), 101).
The identity of the author is uncertain and no trace of his name is to be found in any acrostical combination in the poem. *Heidenheim (Ha-Piyyutim ve-ha-Paytanim, s.v. Judah b. Samuel b. R. Kalonymus, in: Introd. to his Shemini Aẓeret Maḥzor) ascribes its authorship to *Samuel b. Kalonymus he-Ḥasid, the father of *Judah he-Ḥasid of Regensburg. A. Epstein (in Ha-Goren, 4 (1903), 96–98) has sought to identify Samuel b. Kalonymus Ḥazzan as the author.
Originally, the appropriate portion of the Shir ha-Yiḥud was recited in many congregations after the conclusion of the daily service. Some congregations only recited it on the Sabbath. The most prevalent contemporary custom is to recite the entire poem at the conclusion of the service on the eve of the *Day of Atonement, and to chant the appropriate daily section at the start of the morning service on *Rosh Ha-Shanah and the Day of Atonement. Its elimination from the daily and Sabbath services was probably due to the desire not to lengthen the service unduly, though some authorities also quoted the talmudic dictum that no mortal is capable of properly praising the Almighty (A. Lewisohn, Mekorei Minhagim (1846), no. 32). "It is as if an earthly king had a million denarii of gold, and someone praised him as possessing silver ones. Would it not be an insult to him?" (Ber. 33b).
Reifmann, in: Oẓar Tov, 8 (1885), 20–5: A. Berliner, in: Jahresbericht des Rabbiner-Seminars zu Berlin fuer 1908–1909 (1910) (= Ketavim Nivḥarim, 1 (1945), 145–70); A.M. Habermann (ed.), Shirei ha-Yiḥud ve-ha-Kavod (1948), 11–60; Elbogen, Gottesdienst, 81.