Today's reading is Numbers 8-10 (read it in the KJV or NIV)
Today's passage covers the commandment to set up lamps in the tabernacle; the setting apart of the Levites; the first Passover; God's cloud above the tabernacle; the commandment to make silver trumpets; and the Israelites' departure from Sinai.
Imagine the scenario: you've got about two million men, women, and children camped at the base of a mountain. You need to get them all moving in some semblance of order so that they all reach their destination in fighting condition. Furthermore, you have no cell phones, no loudspeakers, no walkie-talkies, no live-coverage broadcast CNN feeds. In fact, you have no modern communication equipment whatsoever. So how do you do it? This is the precise question that arises in Num. 9-10.
The first thing you're going to need is a sign that it's time to pack up and head out. If you left it up to a single man, people might claim he was despotic. After all, the Israelites just left Egypt, where they were under the iron hand of the Pharaoh. The last thing they wanted once they were free was to be ruled by yet another arbitrary commander. On the other hand, if you left the movements up to a committee, they might be camped at Sinai for twenty years while waiting for "the opportune moment."
So they Israelites did what any good, religious, ancient people would do: they trusted God. Unlike many other ancient civilizations, however, God rose to the challenge and answered. God materialized in the form of a cloud over the tabernacle, at the centre of the Israelite camp. When it was time to stay put, the cloud remained hovering over the tabernacle. When it was time to move out, the cloud lifted up and floated over to the new location for the camp. It was that simple: cloud down, stay where you are; cloud on the move, you'd better follow it. (Num. 9:15-23)
I's well and good that the cloud was the signal to move, but if everyone moved at once, there would be chaos in the camps. We've seen the mayhem that can erupt at super-sale days at Future Shop; imagine that multiplied several hundred thousand times. So the Israelites needed a signal on a slightly smaller scale, something more manageable.
Enter Num. 10:1-10. In these verses, God commands the Israelites to build two silver trumpets to sound the assembly and the march. One blast on the trumpet meant it was time for the eastern camps to set out. Two blasts meant the southern camps should follow them. (Num. 10:5-6) There is no indication for the signals for the western and northern camps; we'll just have to assume they worked things out for themselves.
Trumpets were traditional tools to gather assemblies and signal the hour of departure. In the late 15th century, a pilgrim by the name of Pietro Casola noted that on his pilgrimage from Venice to Jerusalem, the ship's captain used trumpets to call the pilgrims back to the ship or to announce imminent departures. So at least two and a half millennia after the Israelites' departure from Sinai, trumpets were still being used in the way God indicated. That's lasting value.
Of course, trumpets could be used for other reasons, and in fact they were. Num. 10:9-10 notes several other times the trumpets should be blown: when going to war, on days of gladness, of days of solemnity, at the beginning of the month, over burnt offerings, and over peace offerings. Or, to paraphrase, there was a lot of trumpet-blowing in the Israelite camp. Especially given that there were daily burnt offerings at the tabernacle, the sound of trumpets would have been nearly as ubiquitous in the Israelite camp as church bells are in a modern European town. It's a good thing God make sure to tell Moses that the blast for journeying should be different from the other ones.
Where were we? Ah, yes. The cloud had lifted, the trumpets had been sounded, and it was time to hitch up the wagons and head out.
Of course, the Israelites had been camped at Sinai for a long time. They arrived in the third month after the Exodus (Ex. 19:1), and didn't leave until nearly a year later. (Num. 10:11 -- the twentieth day of the second month of the second year after the Exodus) They were layabout homebodies by this point, comfortable where they were.
Because of this long sedentary period, God decided it might be best not to tax the Israelites' walking legs too much and only took them on a three-day journey before settling down on the tabernacle again. (Num. 10:33) After all, a journey of forty years begins with a single step. Or, in this case, a single three-day trek. They Israelites would have plenty of time to complain about pebbles in their sandals later. For now, it was best to get them used to walking without straining them overmuch.
In the end, then, Moses had a decent system in place to get the Israelites up and moving: look for the cloud's departure, sound the trumpets, and get the camp moving, hopefully not for too long. Of course, it still must have been fairly chaotic the first few times the Israelites decided to march. There's only so much you can do with two million people and a limited budget. On the other hand, things are easier when you've got God on your side.