Reference

Joel 1:14

Sanctify ye a fast, call a solemn assembly, gather the elders and all the inhabitants of the land into the house of the Lord your God, and cry unto the Lord,
12

The vine is dried up, and the fig tree languisheth; the pomegranate tree, the palm tree also, and the apple tree, even all the trees of the field, are withered: because joy is withered away from the sons of men.

13

Gird yourselves, and lament, ye priests: howl, ye ministers of the altar: come, lie all night in sackcloth, ye ministers of my God: for the meat offering and the drink offering is withholden from the house of your God.

14

Sanctify ye a fast, call a solemn assembly, gather the elders and all the inhabitants of the land into the house of the Lord your God, and cry unto the Lord,

15

Alas for the day! for the day of the Lord is at hand, and as a destruction from the Almighty shall it come.

16

Is not the meat cut off before our eyes, yea, joy and gladness from the house of our God?

Counter-Arguments

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

The Lords Day

The verse calls for a solemn assembly and a fast, which are special acts of worship, but it does not explicitly name or define this occasion as "the Lord's Day" or distinguish it from the seventh day. The command is to gather into "the house of the Lord your God," which could refer to any day of assembly.