“Shittim” (v.1) is where the Jews married pagan women one year earlier (Num.25:1). God had warned them that if they did that, they’d start worshipping pagan gods and He would curse them (Deut.7:1-4). So why’d they do it in Shittim? It was because the king of Moab hired a false prophet named Balaam to curse Israel, but he said he couldn’t (Num.23:1-20). But he really wanted his money, so he taught them to curse themselves by marrying those Moabites. They fell for it (Deut.25:1-3). “Baal” was the false god that pagan nations like Moab worshipped, and Baal was another name for the devil (cf.Mt.12:24). And when those daughters of Moab got the Jews to worship Baal, God cursed them (Deut.25:3,5,9).
It was all Balaam’s doing (Num.31:15), a type of the Tribulation (Rev.2:14). There will be more false prophets in that day leading Jews to worship the devil and his christ, right before Israel enters the kingdom. We see that pictured in Numbers 25 when the Jews did it before entering Canaan.
The number three (Josh. 3:2) is the number of resurrection, since Christ rose on the third day, and there’s going to be a resurrection of Old Testament saints right before the kingdom, something we see typified when the Jews entered the Promised Land after three days.
In that day, the Lord will lead Israel across the Jordan again, into the kingdom (Isa.11:15). So the Jews will be led into the Promised Land here in Joshua by something that represents the Lord, the ark (Josh.3:3). The ark was a box with the law inside (Deut.10:1,2). It had cherubim on top with their wings stretched toward one another, and a mercy seat between (Ex.25:21,22). God sat on it (Ps.99:1), so it was the presence of God, making it a type of Christ, the presence of God in the New Testament. The wood was a type of His humanity (Ex.25:10), the gold of His deity. It had the law inside, as Christ had the law in Him (Ps.40:7,8cf.Heb.10:7).
The Jews were told to follow the ark across the river, but not get too close, so they could know where they were going (Josh.3:4). To lead 2 million people, you have to be ahead of them. That’s a picture of how the 12 had a hard time following the Lord because they were too close to Him (John 14:7-9). It’s hard to believe a man is God if you see Him get tired, hungry, etc. That kept them from knowing the way to the Father (John 14:4-6), just as being too close to the ark would have kept the Jews from knowing the way into the Promised Land. The only other time the Bible mentions “two thousand cubits” (Josh.3:3) is when the Jews were told to stay that far from these ark-bearing Levites (Num.35:1-5).
“Sanctify” here (Josh.3:5) means the same as it did when the Jews came out of Egypt. Then, it meant they had to wash their clothes (Ex.19:10) before entering Canaan. He told them to wash them when they came out of Egypt because He’d just told them they were to be a kingdom of priests (v.6). In the kingdom, Jews will be God’s priests to the world, so they had to wash their bodies (Ex.29:1,4) and their clothes (Num.8:5-7). And the Jews should have gone straight into Canaan after they left Egypt (Deut.1:2) but sinned, so they had to wander 40 years. But now that they are about to enter Canaan, they must wash their clothes again.
“Magnify” (Josh.3:7) means to make larger, as with a magnifying glass. Joshua was Moses’ assistant, but God magnified him by parting the Jordan for him. That’s a type of how the Lord was His father Joseph’s carpenter’s assistant, but God magnified Him at the Jordan (Mark 1:9-11).
The priests were told to “stand still” in the Jordan (Josh.3:8) as the Jews were told to “stand still” before crossing the Red Sea (Ex.14:13,16,21). Moses was also a type of Christ, because that’s how God saves us through Him. That is, Moses did all the work of saving the Jews at the Red Sea; they were just to stand still and watch. Just like Christ did all the work in saving us—we just stand still and believe it!