The Bamidbar Rabbah, a collection of rabbinic teachings on the Book of Numbers, sheds light on this very question. It tells us that the well, a miraculous source of water that accompanied the Israelites throughout their desert journey, was given to them at the beginning of their forty years of wandering. So why is this song mentioned at the end?

To understand, we need to go back a few verses, to Numbers 21:14, which mentions "the book of the Wars of the Lord" and a place called "Vahev...and the tributaries of the Arnon." According to the Bamidbar Rabbah, here, at the tributaries of the Arnon River, God performed incredible miracles for the Israelites, comparable to the parting of the Red Sea (Yam Suf).

But what were these miracles? Imagine a deep ravine, seven mil (a significant distance) across, separating two mountains. To travel from one side to the other, you'd have to descend into the ravine and then climb back up the opposite side. Now, picture the nations hostile to Israel gathering in this ravine, plotting an ambush. Some hid in caves along the ravine walls, while others positioned themselves on rocky outcroppings shaped like breasts – shadayim, as the verse describes it, "And the outpouring of [ve’eshed] the ravines" (Numbers 21:15). Their plan was simple: when the Israelites descended into the ravine, they would be attacked from above and below.

But God had other plans. Instead of allowing the Israelites to descend into the treacherous ravine, He commanded the mountains to move. The breast-like projections from the mountain on the Land of Israel side miraculously entered the caves on the opposite side, crushing all the enemies hiding within! The mountains then shifted, forming a smooth path for the Israelites to cross.

The Bamidbar Rabbah emphasizes that the mountain from the Land of Israel moved, not the one from the land of Moab. Why? Because, it says, the Land of Israel is eager to greet its children. It uses a beautiful metaphor: it's like a maidservant who sees her master's son approaching and rushes out to meet him. This land is eager to welcome the Israelites home.

And the well? It descended into the ravine and swelled, sweeping away the remaining enemies, just as the sea had done in Egypt. As the Bamidbar Rabbah says, this is why the verses about "Vahev by storm [besufa]" and the tributaries of the Arnon are juxtaposed (Numbers 21:14).

The Israelites, however, were completely unaware of these miracles. They simply crossed the mountains on the newly formed path. So, God decided to reveal the extent of His intervention. The well descended into the caves, bringing forth countless skulls, arms, and legs. When the Israelites sought the well, they saw it emerging from the ravine, overflowing with the remains of their enemies.

This is where the song comes in. The Israelites, standing over the ravines, witnessing the miraculous aftermath, sang, "Rise, well, give voice for it!" (Numbers 21:17). They weren't just celebrating water; they were celebrating God's hidden acts of salvation.

The Bamidbar Rabbah asks: Was the well really from "there"? Hadn't it been with them for forty years (Numbers 21:15-16)? The answer, of course, is yes. The well descended to publicize the miracles, to make them known. It was a tangible sign of God's unseen hand.

So, the next time you read about the Israelites wandering in the desert, remember the tributaries of the Arnon. Remember the hidden miracles, the mountains that moved, and the well that revealed God's salvation. It's a reminder that even when we are unaware, God is working on our behalf, performing miracles we may never fully comprehend. And perhaps, like the Israelites, we too should pause and sing a song of gratitude for the unseen wonders in our own lives.