In every prayer, new sparks are sorted out. However, only “on the Shabbat day he shall arrange it” (Leviticus 24:8). That is, the prayers of the entire week do not ascend except on the Shabbat day, [when] the Kohen⁸⁹ shall set it out before G‑d. That is, when the Kohen performs the work during the mussaf prayer of Shabbat day, during the recitation of “Kedusha” (Keter), all the prayers ascend. Ketones Passim, p. 38b

footnotes: ⁸⁹ I.e. the Tzaddik.