Leviticus 9:3

And to the children of Israel spoke he, saying: Take for yourselves a kid of the goats, because Satana resembles him, lest he recount against you the accusation concerning the kid of the goats, which the sons (tribes) of Jakob killed, (Gen. xxxvii. 31,) and offer him for a sin offering; and a calf, because ye worshipped the calf, (Exod. xxxii. 4,) and a lamb of the year, that there may be for you a memorial of the righteousness of Izhak, whom his father did bind as a lamb, both of them perfect, for a burnt offering;

And unto the children of Israel thou shalt speak. This means that Aaron is to speak to them thus, as it was His wish that Aaron should be the one who commands in the name of G-d, and that he should be the one who would bring the offerings, in order to elevate him in the eyes of the people. The correct interpretation is that the expression and unto the children of Israel thou shalt speak, means you [Aaron] and the elders mentioned [in Verse 1], since it was for that purpose that he called them,. so that they should speak to the children of Israel, as in the verse, And Moses called for all the elders of Israel, and said unto them: Draw out [and take you lambs]. Or it may be that [Moses] said to each of the elders, and unto the children of Israel thou shalt speak [the singular word thou thus referring to each one of the elders]. Accordingly, the meaning of the section is as follows: and he [Moses] said to Aaron: Take thee etc., and to [each of] the elders he said, and unto the children of Israel thou shalt speak. For one who speaks to many people usually addresses his command to each person individually, something like that which it is said, And I commanded you at that time, saying etc.: Ye shall pass over armed before your brethren. There are many such cases in the Book of Deuteronomy [where Moses speaks to the whole congregation, when his message is actually addressed to each person individually].
Now Rabbi Abraham ibn Ezra wrote that the verse, And Moses said: This is the thing which the Eternal commanded that ye should do, means that “Moses had already told them, this is the thing.” If so, it is possible that the meaning of the verses be as follows: Moses called Aaron and his sons and the elders of Israel, and Moses said: This thing which the Eternal has commanded me ye should do, that the Glory of the Eternal may appear unto you; and he said unto Aaron: Take thee a bull-calf etc.; and unto the children of Israel thou shalt speak, saying: Take ye a he-goat for a sin-offering etc. Thus [Moses] spoke briefly at first [as in Verse 6] and then explained himself at the end [in Verses 2-4].
But this is not correct. Rather, after Moses had mentioned to them the offerings [which they were required to bring on that day], and they brought that which Moses commanded, he said to them again, This is the thing which the Eternal …