Q. It is known that if one sings the shira of Oz Yashir said every day during Shacharis, Hashem will forgive his sins. Does that have to be the complete shira?

A. Indeed, the Zohar quoted by the Mishna Berura (51: 17) teaches that most important and essential principle.

Horav Shlomo Miller’s Shlit’a opinion is that one should indeed sing it complete. (without disturbing others).
It finishes at the verse “Hashem Imloch Leolam Vaed.

Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a.