AE 54, 55 - portions of Revelation 1:10

AE 54
On the Lord's day.
That this signifies, Divine influx at the time,
is evident from the signification of the Lord's day,
as being when the Lord instructs a person,
thus when He enters by influx.
The Lord's day is the day of the sabbath,
and the sabbath in the Ancient Churches,
which were representative churches,
was the most holy thing of worship,
because it signified the union of the Divine and Human in the Lord,
and so also the conjunction of His Divine Human with heaven.
But after the Lord united His Divine with His Human,
then that holy representative ceased,
and that day became a day of instruction.
For this reason revelation was made to John on the Lord's day;
revelation, in this case, is instruction concerning the state of the church.

AE 55
And I heard behind me a great voice, as of a trumpet.
The reason why "behind me" signifies clearly (or manifestly), is
because those things that flow from heaven into the affection of a person,
flow into the back part of the head,
and thus enter clearly into his perception;
for the things which enter into the affection are perceived clearly,
all the life of perception being from that source;
but the things that flow from heaven immediately into the thought,
flow into the part above the forehead.
It is therefore evident what is signified by John's hearing behind him,
and by his afterwards turning to see the voice which spake with him.
The reason why a trumpet, or horn,
signifies Divine truth to be revealed from heaven, is,
because Divine truth is sometimes so heard when it flows down from the Lord
through the heavens to a person;
for it becomes louder in its descent and thus flows in.
But it is heard in this way only in the beginning,
by those to whom Divine truth is to be revealed in the ultimate sense,
which is representative of interior things;
afterwards it is heard as a human voice.