Yedid Nefesh
Yedid Nefesh is the title of a piyyut and zemer. It is usually sung on Shabbat.
Origin
This poem is commonly attributed to the sixteenth-century Sephardic kabbalist Rabbi Elazar ben Moshe Azikri, who first published it in Sefer Charedim. Still, Azikri did not claim authorship of it, and there have been other suggested authors. Azikri's philosophy centred around the intense love one must feel for God, a theme evident in this piyyut. The first letters of each of the four verses make up the four-letter name of God, known in English as the tetragrammaton. Various different textual readings appear in contemporary siddurim; the version printed in Siddur Rinat Yisrael and some other siddurim is the text that appears in Sefer Charedim.Traditions
There is a custom to sing 'Yedid Nefesh' between Mincha on Friday and the beginning of Kabbalat Shabbat.Many Hasidic Jews say or sing it every morning before beginning the pesukei dezimra section of Shacharit in order to arouse their love of God in preparation for the pesukei dezimra in Nusach Sefard siddurim.