Samuel was just a child in the service of God as overseen by the High Priest Eli. He had been dedicated to God by his mother, as she had promised in a prayer, so he was living with the priests. Most translations of 1 Samuel 3:3 say that after Eli began losing his sight but before the enemies of Israel had overtaken the land, Samuel was sleeping in the temple of the Lord, where the ark was. Why was he sleeping there?
The first question, really, should be where was there? The passage specifically mentions the “temple” or dwelling place of the Lord. This was up to eighty years before the building that is typically called the Temple was built. It could not, then, be Solomon’s Temple. There is a separate word, though, for the Tabernacle or tent constructed in the wilderness. This is the first use of the word hakal in scripture. The Tabernacle was usually referred to by the word mishkan (dwelling place) or ohel (tent). In fact, the former word was specifically used in the previous chapter to refer to the place where the priests worked. So was Samuel sleeping in the Tabernacle, or a separate building?
The verse also specifies that it was “where the ark was.” While there are arks of varying sizes and importance in the Bible, the implication is that this was the Ark of the Covenant. That, in itself, makes it clear that Samuel was asleep in the Tabernacle. Why would he, or anyone, sleep in that holy place?
Earlier in the book, Samuel’s mother “lent” him to the Lord for life. He ministered to the Lord in the presence of Eli (3:1). This, in itself, is unusual. Only the descendants of Levi were to serve in the Tabernacle and to make sacrifices. Here is Samuel, an Ephrathite (either a descendant of Ephraim or of Bethlehem in the territory of Benjamin), serving in the Tabernacle. King Saul didn’t wait for Samuel to offer a sacrifice, but did so himself. He lost his throne because of that, and yet Samuel (possibly of the same tribal line as Saul) was authorized to offer the same sacrifices. (1 Sam 13) Perhaps it is because of his being lent to the Lord for life that he was authorized to enter the Tabernacle and make burnt offerings. Whatever his lineage, he was ministering to the Lord, which would mean his sleeping place was in the tabernacle.
Another clue might be in the reference in the early part of the verse. This was “before the lamp of God went out.” That phrase probably refers to the Philistine conquest of Israel, when they would have suspended the worship of God. Nevertheless, it may give a reason for Samuel’s presence. The Law of Moses required that the lampstand in the Tabernacle be kept burning from evening to morning. (Lev 24:4) As part of his ministry, Samuel may have had the responsibility for the lamps. As a youth, he may not have been expected to stay awake all night, and so was allowed to sleep in the Tabernacle. As long as he made sure the lamps stayed burning, he might be allowed to sleep.
Whatever Samuel’s reason for sleeping there, we can know two things. First, God spoke to Samuel as he slept where he did. This is at least a tacit approval of Samuel’s sleeping in the temple. Sometimes we are quick to judge people for doing things that we think should be wrong. God does not necessarily agree with our standards. Some might say that Samuel had no business being where he was, and even less business sleeping there. God didn’t say, “Samuel, what are you doing here?” He only said, “Samuel.”
Second, there are some circumstances in which someone from other than the tribe of Levi was allowed to fulfil the priestly offices. This gives Christians hope. “For it is evident that our Lord sprang out of Juda; of which tribe Moses spake nothing concerning priesthood.” (Heb 7:14) Circumstances allow our High Priest to serve in our stead. Without those circumstances, we have no forgiveness.