Halakhah zu Schemot 15:1

During the Geonic era, some had the custom to add verses from the Torah and from Neḥemia, such as Va-yevarekh David (1 Divrei Ha-Yamim 29:10-13 and Neḥemia 9:6-11) and Shirat Ha-yam, the song that Moshe and the people of Israel sang to God after the splitting of the sea (Shemot 15:1-18). Although the main parts of Pesukei De-zimra are taken from Tehilim (as stated in the words of Barukh She-amar) there is no problem with adding Va-yevarekh David, which is not from Psalms, or Shirat Ha-yam, which is Moshe’s song (Peninei Halakha: Prayer, ch. 14 n. 3).

[The Psalm] Mizmor Lesodah should be said while standing and with joy for [this psalm] represents the Thanksgiving sacrifice.⁵The sacrifice offered as a thanksgiving for being saved from illness or catastrophe. Similarly, from Vayevarach David until atah hu Hashem Ha'elokim, should be said while standing. The Shirah,⁶I.e., אָז יָשִׁיר (Ex. 15:1–9). too, should be said while standing, with concentration and with joy. During the berachah—Yishtabach, you should also stand.