Adon Olam

Adon Olam (Hebrew: אֲדוֹן עוֹלָם; "Eternal Lord" or "Sovereign of the Universe") is a strictly metrical hymn in the Jewish liturgy written in lines of eight syllables; more precisely, each line is composed of two segments of one yated and 2 tenu'ot, which indeed makes 8 syllables. It has been a regular part of the daily and Shabbat (Sabbath) liturgy since the 15th century.