Mishnah Berurah — משנה ברורה

By day - For the sacrifices were only offered by day. But the passage of the basin and the passage of the removal of the ashes may be said before the day. And if one does not have time, he may also say the passages of the sacrifices at night. And [regarding] whether it needs to be said while standing, see in siman 48, Mishnah Berurah se'if katan 1. It's written in the Sh'la, that on Shabbat and Yom Tov, one should not say the "Yehi Ratzon" ("May it be Your will..."), because voluntary sacrifices are not offered on those days; but [to recite] the passages [of the voluntary sacrifices], you don't lose out anything by saying them, it is like reading from the Torah. Nevertheless, if he is a Torah scholar, it is better for him to involve himself in learning the passages [that relate to] that day. One who is a mourner should not recite the passage of the sacrifices (because he is forbidden to learn Torah).