Midrash sobre Êxodo 17:5

Reuben went in the days of harvest, etc. Raba b. Isaac said in the name of Rab: "Infer from this that the righteous do not stretch their hands out to robbery." What were the dudaim which Reuben found? Rab said: "They were mandrakes," and Samuel said: "Violet flowers." R. Alexandri said: "Those who occupy themselves with the Torah for its own sake [for no selfish ends] cause peace to reign in the heavenly household and in the household here below," as it is said (Is. 27, 15) "If he would but take hold of my strength, make peace with me, make peace with me." And Rab said: "He is considered as if he had built both palaces of heaven and earth," as it is said: (Ib. 51, 16) "And I have placed My words in thy mouth, and with the shadow of My hand have I covered thee: To plant the heavens and lay the foundations of the earth." R. Jochanan said: "He also protects the world, as it is said (Ib.) "With the shadow of My hand have I covered thee." And Levi said: "He brings nearer the redemption, as it is said (Ib.) To say to Zion, Thou art My people." Resh Lakish said: "He who teaches the Torah to his neigbor's son, is considered by Scripture as if he had created him," as it is said: (Gen. 12, 5) "And the persons they had obtained Charan." R. Elazar said: "He is considered as the creator of the law, as it is said: (Deut. 29, 8) Keep ye, therefore, the words of the covenant, and do them." And Raba said: "He is considered as the creator of himself," as it is said, "And do them; do not read otham (them), but atem, (ye yourselves)." R. Abahu said: "He who causes his neighbor to do a meritorious act, is considered by Scripture as if he himself has done it, for it is said: (Ex. 17, 5) "And take in thy hand thy staff wherewith thou smotest the river, and go." Did he, then, smite the river? Did not Aaron do this? But this is to teach thee that whoever causes his neighbor to do a meritorious act is considered by Scripture as if he himself had done it."

The sapphire staff with which He brought the plagues upon the Egyptians in Egypt and killed them at the Red Sea (was an instrument for punishment). But they knew that it was an instrument that performed miracles as well. And the Lord said unto Moses: “Pass on before the people, and take with thee of the elders of Israel, and thy rod, wherewith thou smotest the river” (Exod. 17:5), He did so because of their rebelliousness.

And Moses took his wife and his sons, and set them upon an ass (Exod. 4:20). The singular form ass is employed here, as when a man says: “Lead out the animal” (though he may have many). And Moses took the rod of God in his hand (ibid.). The Holy One, blessed be He, said to him: Take this rod in your hand, for with it you will be able to perform any miracle you desire. He struck the Nile with it, as it is said: And thy rod, wherewith thou smotest the river, take in thy hand (Exod. 17:5). Sometimes Scripture calls it the rod of the Lord and at other times thy rod.