Pesukei dezimra (פְּסוּקֵי דְּזִמְרָא pǝsûqê ḏǝzimrāʾ "Verses of praise"; Rabbinic Hebrew: פַּסוּקֵי הַזְּמִירוֹת pasûqê hazzǝmîrôṯ "Verses of songs), or zemirot as they are called in the Spanish and Portuguese tradition, are a group of prayers that may be recited during Shacharit (the morning set of prayers in Judaism). They consist of various blessings, psalms, and sequences of other Biblical verses. Historically, reciting pesukei dezimra in morning prayer was a practice of only the especially pious. Over the course of Jewish history, their recitation has become widespread custom among all of the various rites of Jewish prayer.
The goal of pesukei dezimra is for the individual to recite praises of God before making the requests featured later in Shacharit and the day.
The first source for pesukei dezimra is in the Babylonian Talmud, where it is described as non-obligatory (performed by some people but not others):
Rabbi Yosei said: May my portion be among those who eat three meals on Shabbat. Apropos this statement of Rabbi Yosei, the Gemara cites additional declarations. Rabbi Yosei said: May my portion be among those who complete hallel every day. The Gemara is surprised at this: Is that so? Didn’t the Master say: One who reads hallel every day is tantamount to one who curses and blasphemes God. He displays contempt for hallel by not reserving it for days on which miracles occurred. The Gemara answers: When we say this statement of Rabbi Yosei, we are referring to the verses of praise [pesukei dezimra], recited during the morning service, not to hallel (Psalms 113–118) recited on special days.
Later commentaries explain what pesukei dezimra consists of: Rashi said it means psalms 148 and 150, Saadia Gaon said it means psalms 145, 148, 149, 150, while Menachem Meiri and Maimonides said it means all of psalms 145-150. Nowadays, it is customary for pesukei dezimra to include psalms 145-150 as well as several other psalms, recitations, and blessings before (Barukh she'amar) and after (Yishtabach) pesukei dezimra.