Another matter, “send you men, that they may scout.” “Miriam and Aaron spoke against Moses” (Numbers 12:1) and then: “Send you [men].” This is what the verse said: “They do not know and they do not understand, for their eyes are smeared and don’t see” (Isaiah 44:18). What did He see that led Him to say: “Send you men” after the incident involving Miriam?
It is, rather, that it was anticipated before the Holy One blessed be He that they would speak slander about the Land. The Holy One blessed be He said: ‘So they will not say: We did not know the punishment for slander.’ That is why the Holy One blessed be He juxtaposed one matter to the other; because Miriam spoke against her brother and was stricken with leprosy, so that all would know the punishment of slander, so that were they to seek to say slander, they would look upon what befell Miriam.
Nevertheless, they did not wish to learn. That is why it is stated: “They do not know and they do not understand, for their eyes are smeared and don’t see.”