זוהר ויקרא — דף לח ע”א

We first learn that the Community of Israel is blessed through the priest, that Israel is blessed through the priest, and that the priest himself is blessed through the supreme priest. On the verse "Remember Your mercies, O Lord, and Your kindnesses, for they have been from of old," it is explained that Jacob and Abraham are the ones whom the Holy One, blessed be He, took from the world and raised on high, making of them a holy chariot to protect the world. Isaac is not mentioned here because he remains to avenge the enemies of his children, as indicated by the verse "Stir up Your might." It is further explained that at the creation of the world, Isaac alone was not enough to sustain it, so Abraham was added, and finally Jacob, who joins Isaac and sustains the world — this is the hidden meaning of the verse "on the day that the Lord God made earth and heaven."<br />
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On the eighth day, after the seven days of consecration, Aaron needed to be perfected from those seven days and to be corrected for his earlier sin. He was therefore told to take a calf as a sin offering, precisely to atone for that same calf which Israel had sinned with. The question is then asked why "a bull calf and not a cow" — the answer being that it is not fitting to offer the cow a gift drawn from herself, like one who sends a gift to the king: it must come from another house, not from the king's own house.<br />
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The "sin offering" comes to purify Aaron from that same sin, while the ram is offered "as a whole burnt offering, unblemished" — the expression actually referring to two rams: Isaac's ram at the Binding, mentioned twice in the text, in "Abraham lifted up his eyes and looked, and behold, a ram" and then "Abraham went and took the ram." As for Israel, it is said "take a goat as a sin offering" and not a calf, because Israel had already received its punishment for the sin of the golden calf in various ways, so that its offering is a calf as a burnt offering and not as a sin offering.<br />