The Pesukei D'Zimra, the daily set of psalms recited in the beginning of Shacharit, begin with the blessing "Baruch She'amar" and end with the blessing "Yishtabach."
It is written in the Mishna, "The third wine cup is poured for him, and he recites a blessing for the food that he ate. For the fourth cup, he finishes reciting the Hallel and says the blessing 'of the poem'" [Pesachim 117b]. The Talmud gives two opinions to explain what the "poem" is. Rabbi Yehuda says, this is "Let G-d be blessed." And Rabbi Yochanan says it is the prayer, "Nishmat Kol Chai."
"Let G-d be blessed" – Yehallelucha – is the blessing that we usually recite at the end of Hallel, which ends with the praise, "a king who is exalted with praise."
"The soul of every living creature" – Nishmat – ends with the blessing "Yishtabach." On weekdays, this is shortened to a single paragraph in order to avoid clashing with needs of work. On Shabbat and a holiday it is left in its original longer form.
In any case, the blessing "Baruch She'amar" is not mentioned explicitly in the Talmud. The author of the Pri Chadash wonders about this. "I do not understand: How could the Geonim add a new blessing after the Talmud was finished and sealed?" [Orach Chaim 51].
Others disagree with Pri Chadash and they have shown that early sources exist for the blessing Baruch She'amar. The Mordechai implies that it is a decree made by the Anshei Knesset Hagedola (end of the tractate of Pesachim). The blessing also appears in "Shiltei Hagiborim" in the name of the Talmud Yerushalmi (Berachot Chapter 5). Avudraham also quotes the Yerushalmi, although this does not appear in our version of the Talmud. The TAZ writes in the name of Tola'at Yaacov, who quotes Or Zarua, that "this praise for G-d was established by the Anshei Knesset Hagedola based on a note that fell from heaven."
We should note that even though this blessing is not mentioned as such in the Talmud, parts of it do appear in various places. (1) The Mishna lists as one of the blessings recited when not enough rain has fallen, "You are blessed, He who has mercy on the land" [Taanit 2:4). (2) "Blessed is He who declares, acts, makes decrees, and fulfills them" [Berachot 56b]. (3) Shimon Ben Shatach, in the trial of a slave of King Yanai, is reported to have said, "He who spoke, and the world came into existence" [Sanhedrin 19a]. (4) The phrase "blessed is He who performs primordial acts" appears in Berachot 9a.
It is important to understand the origin of the blessing Baruch She'amar not only for historical reasons and not only as a way to know how the prayer developed. This is also an important halachic question. The source of the prayer is important in that it can have an effect on the derived laws and customs, as we will see in future articles.
"And with the Poems of Your Slave David"
The blessing Baruch She'amar gives an explanation of the importance of the Pesukai D'Zimra. "You are blessed, G-d... You are praised and glorified in the words of Your righteous people and slaves, and in the songs of Your slave David. We will praise you, Our G-d, with praise and song..." The "songs of your slave David" – that is, the Psalms – serve as one of the most central sources for describing the praise of the Holy One, Blessed be He. We too praise G-d mostly by quoting the Tehillim (as we will see, it is likely that the original version of Pesukai D'Zimra was made up exclusively of passages from Tehillim).
The Psalms have a very unique importance, as is explained here as part of the instructions for one who has repented: "He should attach himself very closely to the Psalms written by King David, which are great and have the power to instill a love for the Creator in the heart of a man" [Noda B'Yehuda 141].
Pesukai D'Zimra are not only praise for the Almighty. They are not simply a statement of praise and glory. The Pesukau D'Zimra consist of poems and praise dedicated to the Holy One, Blessed be He, and they have a unique power to excite us and bring us to a love of G-d. This means that in addition to their importance as a way of praising the Almighty (as we saw in a quote from the BACH in an earlier article) and aside from the fact that they are part of the preparation for prayer which will help us reach a state of happiness, they also contain elements that will help us achieve a state of love for the Creator and a desire to become attached to Him. Praise, happiness, and love will all bring us to the entrance to the innermost chamber of the King.