Yishtabach
Yishtabach is a Jewish prayer of acclamation recited at the end of Pesukei Dezimra during the Jewish morning prayer service, Shacharit. Yishtabach precedes the recitation of Chatzi Kaddish, which in turn precedes Barechu. As a component of Pesukei Dezimra, Yishtabach is preceded by the recitation of Barukh She'amar. Both Yishtabach and Barukh She’amar are blessings, which supports the notion that Pesukei Dezimra is a single, unified prayer for praising God. The author of Yishtabach is unknown; tradition attributes it to Solomon, as the initial letters of words 2–5 form an acronym of his Hebrew-language name "שְׁלֹמֹה".
The blessing highlights the number fifteen: fifteen expressions of praise at the start and fifteen words in the closing line. This alludes to a divine name of God, Yah, that, in Gematria, is assigned a value of fifteen; there are also fifteen Songs of Ascent in the book of Psalms. Rabbi Ron Isaacs argues that there are two themes of Yishtabach: God's power and might are deserving of praise and adoration, and that one must continually praise God.
In the Ashkenazic rite, Yishtabach is usually recited while standing. This practice follows a ruling made in the Mishnah Berurah of standing during Barukh She’amar, and since Yishtabach concludes Pesukei Dezimra, they are recited in the same manner. On Shabbat, some Jewish communities, regardless of their rite, sit during the recitation of Yishtabach. In most Sephardic communities, the blessing is always recited while seated.