Sardis is the slumbering church. It has but a name, and is in reality, dead. Jesus warned that He will "come as a thief" on those who are not watching.
In Leviticus 6:8 - 13, the LORD commanded how the burnt-offering was to be kept. The burnt-offering was to be on the altar "all night unto the morning", and He commanded that "the fire on the altar shall be kept burning thereon" (v9). The fire was so important that the LORD emphasized it again in verses 12 and 13.
"the fire upon the altar shall be burning in it; it shall not be put out" (v12),
"the fire shall ever be burning on the altar; it shall never go out" (v13).
We so often focus on the offering that we forget the fire. We think the offering is the important thing, but somehow, the LORD placed more emphasis on the fire - that it must not go out.
When the priests were serving in the Second Temple, they were sometimes guilty of not watching the fire and allowing it to go out. The High Priest would randomly make his rounds to make sure that the priests were performing their duties and faithfully watching the fire as the LORD commanded. When the High Priest discovers a sleeping priest, he would set fire to the priest's garments. In no time at all, the sleeping priest would be running around amok and naked in the temple, and all the other priests on duty will see his shame. The High Priest is therefore also nicknamed the "thief in the night".
Jesus says "Behold, I come as a thief. Blessed is he that watcheth, and keepeth his garments, lest he walk naked, and they see his shame" (Rev 16:15). Jesus is our Great High Priest (Heb 4) and we are the royal priesthood (1Pet 2:9). When the Son of Man returns, will He find faith on the earth? Will He have to set fire on our garments that we awake from our slumber? Will we be caught sleeping and not watching the fire?
To those who are slumbering and not watching -- He comes as a thief, and we will not know the hour of his visitation; but we are not in the darkness, that the day should overtake us as a thief (1Th 5:4). Let us therefore do what the LORD has commanded -- to watch the fire of our offering that it does not go out, even in these times. When the Son of Man returns, my fire will be strong and I will be found watching for His return.
