We read that the Lord showed him a tree, which when he had cast into the waters, the waters were made sweet. In this we discern the same union of Divine grace with human energy and use of means, as in all medicine, and indeed all uses of the divinely enlightened intellect of man. It would have been easy to argue that the waters could only be healed by miracle, and if God wrought a miracle what need was there of human labour? There was need of obedience, and of the co-operation of the human will with the divine. We shall see, in the case of the artificers of the tabernacle, that God inspires even handicraftsmen as well as theologians--being indeed the universal Light, the Giver of all good, not only of Bibles, but of rain and fruitful seasons. But the artisan must labour, and the farmer improve the soil.
Shall we say with the fathers that the tree cast into the waters represents the cross of Christ? At least it is a type of the sweetening and assuaging influences of religion--a new element, entering life, and as well fitted to combine with it as medicinal bark with water, making all wholesome and refreshing to the disappointed wayfarer, who found it so bitter hitherto.
The Lord was not content with removing the grievance of the hour; He drew closer the bonds between His people and Himself, to guard them against another transgression of the kind: "there He made for them a statute and an ordinance, and there He proved them." It is pure assumption to pretend that this refers to another account of the giving of the Jewish law, inconsistent with that in the twentieth chapter, and placed at Marah instead of Sinai.[30] It is a transaction which resembles much rather the promises given (and at various times, although confusion and repetition cannot be inferred) to Abraham and Jacob (Gen. xii. 1-3, xv. 1, 18-21, xvii. 1-14, xxii. 15-18, xxviii. 13-15, xxxv. 10-12). He said, "If thou wilt diligently hearken to the voice of the Lord thy God, and wilt do that which is right in His eyes, and wilt give ear to His commandments, and wilt keep all His statutes, I will put none of the diseases upon thee which I have put upon the Egyptians, for I am the Lord which healeth thee." It is a compact of obedient trust on one side, and protection on the other. If they felt their own sinfulness, it asserted that He who had just healed the waters could also heal their hearts. From the connection between these is perhaps derived the comparison between human hearts and a fountain of sweet water or bitter (Jas. iii. 11).
But certainly the promised protection takes an unexpected shape. What in their circumstances leads to this specific offer of exemption from certain foul diseases--"the boil of Egypt, and the emerods, and the scurvy, and the itch, whereof thou canst not be healed" (Deut. xxviii. 27)? How does this meet the case? Doubtless by reminding them that there are better exemptions than from hardship, and worse evils than privations. If they do not realise this at the spiritual level, at least they can appreciate the threat that "He will bring upon thee again all the diseases of Egypt which thou wast afraid of" (Deut. xxviii. 60). To be even a luxurious and imperial race, but infected by repulsive and hopeless ailments, is not a desirable alternative. Now, such evils, though certainly not in each individual, yet in a race, are the punishments of non-natural conditions of life, such as make the blood run slowly and unhealthily, and charge it with impure deposits. It was God who put them upon the Egyptians.
If Israel would follow His guidance, and accept a somewhat austere destiny, then the desert air and exercise, and even its privations, would become the efficacious means for their exemption from the scourges of indulgence. A time arrived when they looked back with remorse upon crimes which forfeited their immunity, when the Lord said, "I have sent among you the pestilence after the manner of Egypt; your young men have I slain with the sword" (Amos iv. 10).