Pesukei D'Zimrah

Pesukei dezimra (Hebrew: פְסוּקֵי דְּזִמְרָא‎, P'suqế dh'zimra "hymnal verses") or zemirot, as they are called in the Spanish and Portuguese tradition, are a group of praises that may be recited daily during Jewish morning services. They consist of various blessings, psalms, and sequences of verses. Historically, pesukei dezimra was a practice of only the especially pious. However, it has since become a widespread custom among even the laymen in all of the various rites of Jewish prayer.

The purpose of pesukei dezimra is so an individual will recite praises of God prior to making requests of God in prayer which take place later during Shacharit and throughout the day.

The first source for Pesukei Dezimra is in the Babylonian Talmud, Shabbat 118b, illustrating it is not an obligation ("May my portion be"):

Rabbi Jose said: "May my portion be among those who complete Hallel every day."
- Is this possible? For the master has said: "He who reads Hallel every day is a curser and blasphemer!"
- It (Rabbi Jose's statement) is said regarding Pesukei Dezimra.

Babylonian Talmud, Berakhot 32b alludes to the name "verses of praise", real prayer (tefillah) comes later:

A person should first recount the praise of the Holy One, blessed be He, and then pray

Later commentaries to this line explain what Pesukei Dezimra consists of: Rashi said it means Psalms 148 and 150, while Meiri 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 and recitations.

For a long time, these prayers remained optional. But Maimonides said that prayer should be recited in an upbeat mood, and as a result, these prayers became a part of the regular service. Maimonides also said that these prayers should be recited slowly and wholeheartedly, and that rushing through them as many who recite them daily do defeats their purpose.

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Wikipedia