Here is the advice given to the Moabites (those who are fleeing)—these displaced persons who are fleeing in terror from this huge juggernaut of an army that is sweeping down against them.
The Arnon is a river that empties into the Dead Sea, that goes through Moab, flows west and into the Dead Sea. So it is big enough that, at certain times of the year, it has to be forded. There's water in it and so they have to ford across it in their fleeing.
These displaced persons are heading generally south, but they are mulling around in confusion—they're terrified, frightened, they really don't know what to do. So that's what they're doing at the fords of Arnon. "What should we do? Where should we go? Maybe we ought to go to Zoar? It's a little place, you see nobody will pay any attention to us, if we're there." But they're admonished by God to make an offering—thus the mention of the word "lamb"—to the ruler of the land.
Now who is the ruler of the land? It has to be Christ, because that is where His church is. He is governing His church and He is admonishing the Moabites to make an offering. He is saying, "pray, cry out for mercy" (is what God is saying)—to the ruler of the land, to Jesus Christ. The offering is to go through Selah. That's what it says: "From Selah to the wilderness," because that's where God's outcasts are. But He tells them, "Be sure nobody sees you, hide them, hide my people, don't betray where my people are," and then he encourages them. He says "Hang on, it's almost over. Christ is coming and it's but a short time when that will take place." That's what verse 5 is about.
