Leviticus 23:26

“And the Lord spake unto Moses, etc.] This phrase, which is a kind of preface to each precept, seems to be used to distinguish one from another, as the preceding one from the feast of Pentecost; and here, the day of atonement from that of the blowing of the trumpets; and afterwards, the feast of tabernacles from the day of atonement; the reason why it is not used before the feast of Pentecost seems to be, because, as Aben Ezra observes, that depended upon the wave sheaf, and was reckoned from it: saying; as follows.”

“On the tenth day of the seventh month the day of atonement was to be observed by a holy meeting, by fasting from the evening of the ninth till the evening of the tenth, by resting from all work on pain of death, and with sacrifices, of which the great expiatory sacrifice peculiar to this day had already been appointed in ch. 16, and the general festal sacrifices are described in Num 29:8-11. (For fuller particulars, see at ch. 16.) By the restrictive אך, the observance of the day of atonement is represented a priori as a peculiar one. The אך refers less to "the tenth day," than to the leading directions respecting this feast: "only on the tenth of this seventh month...there shall be a holy…”