FreeGrace2 said:
When Paul mentions "day of the Lord" in v.1
Do I need to provide reading lessons here?
1 Concerning
the coming of our Lord Jesus Christ and our being gathered to him, we ask you, brothers and sisters,
2 not to become easily unsettled or alarmed by the teaching allegedly from us—whether by a prophecy or by word of mouth or by letter—asserting that the day of the Lord has already come.
3 Don’t let anyone deceive you in any way,
for that day will not come until the rebellion occurs and the man of lawlessness is revealed, the man doomed to destruction.
It should be quite obvious to anyone competent in the English language that the red words in v.1 is what Paul was referring to in the red words in v.3.
So, from the context, "THAT day" in v.3 refers back to "coming of our Lord Jesus Christ". What else could Paul be referring to?