Reference

Leviticus 23:40

And ye shall take you on the first day the boughs of goodly trees, branches of palm trees, and the boughs of thick trees, and willows of the brook; and ye shall rejoice before the Lord your God seven days.
38

Beside the sabbaths of the Lord, and beside your gifts, and beside all your vows, and beside all your freewill offerings, which ye give unto the Lord.

39

Also in the fifteenth day of the seventh month, when ye have gathered in the fruit of the land, ye shall keep a feast unto the Lord seven days: on the first day shall be a sabbath, and on the eighth day shall be a sabbath.

40

And ye shall take you on the first day the boughs of goodly trees, branches of palm trees, and the boughs of thick trees, and willows of the brook; and ye shall rejoice before the Lord your God seven days.

41

And ye shall keep it a feast unto the Lord seven days in the year. It shall be a statute for ever in your generations: ye shall celebrate it in the seventh month.

42

Ye shall dwell in booths seven days; all that are Israelites born shall dwell in booths:

Counter-Arguments

The strongest case that this verse does not belong in this theme.

First Day of the Week

The verse explicitly mentions "the first day" but does not specify "of the week." It refers to the first day of a seven-day rejoicing period, not the first day of a weekly cycle.