The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in Parashat Toledot (Shana Sheniya, 6), notes that the Yishtabah prayer, with which we conclude the Pesukeh De’zimra section of the morning prayer service, contains thirteen expressions of praise for God ("Shir U’shbaha Hallel Ve’zimra Oz U’memshala…"). These thirteen expressions, he explains, correspond to the thirteen divine attributes of mercy. As such, one should not make any interruption in the middle of the recitation of these thirteen expressions. If a person sees as he begins Yishtabah that the Hazzan will soon be reciting Kaddish or Kedusha, he should not begin the thirteen expressions of praise until after Kaddish or Kedusha. This ensures that he will be able to recite the thirteen expressions without having to interrupt for the responses to Kaddish or Kedusha.
Nevertheless, the Ben Ish Hai writes, although the thirteen expressions should be recited without interruption, there is no requirement to recite them in a single breath. One must, in the Ben Ish Hai’s words, recite them "pleasantly and calmly," and not hurriedly. Therefore, one should recite the thirteen expressions slowly without rushing to complete them in a single breath.
