And he cried to the LORD, and the LORD showed him a log, and he threw it into the water, and the water became sweet.
There the LORD made for them a statute and a rule, and there he tested them, saying, “If you will diligently listen to the voice of the LORD your God, and do that which is right in his eyes, and give ear to his commandments and keep all his statutes, I will put none of the diseases on you that I put on the Egyptians, for I am the LORD, your healer.”
Then they came to Elim, where there were twelve springs of water and seventy palm trees, and they encamped there by the water (Exodus 15:25-27 ESV).
So 1) someone counted all the springs and trees, 2) recorded the numbers, and 3) preserved this record under the inspiration of the Holy Spirit.
And 4) repeated it a second time:
And they set out from Marah and came to Elim; at Elim there were twelve springs of water and seventy palm trees, and they camped there (Numbers 33:9 ESV).
Who cares about the numbers? Or even the presence of springs and trees? Why not just say they camped at an oasis?
But the context of the whole Bible indicates this really shouldn’t surprise us. Genesis 2 begins creation with trees by rivers of water. And the last book of the Bible ends that way:
Then the angel showed me the river of the water of life, bright as crystal, flowing from the throne of God and of the Lamb through the middle of the street of the city; also, on either side of the river, the tree of life with its twelve kinds of fruit, yielding its fruit each month. The leaves of the tree were for the healing of the nations (Revelation 22:1-2 ESV).
Within this overarching pattern, we have a story of seventy nations (Genesis 10) and the twelve tribes of Israel appointed as a kingdom of priests to them.
Twelve springs of water feeding seventy palm trees. In God’s providence the oasis was a message about Israel’s calling.
And in the immediate context of the promise about diseases, it clarifies the situation. God promises that none of Egypt’s diseases will fall on them but then, lest they think they are called to be healthy in a sick world, makes it clear that they are to be a source of healing water. The river feeds the trees to heal the nations.