Or HaChaim on Exodus 32:5/אור החיים על שמות ל״ב:ה׳

1 וירא אהרון, And Aaron saw, etc. He "saw" something amazing; although he had only thrown gold into the fire, a calf emerged.

2ויבן מזבח לפניו, he erected an altar in front of it, etc. It is noteworthy that the Torah did not write: ויבן לפניו מזבח. Had the Torah used the sequence of words we just mentioned this would have indicated that Aaron built the altar in the golden calf's honour. As it is the proximity of the golden calf to the altar Aaron built was purely incidental. Aaron's intention was totally Heaven-oriented. According to the Zohar volume 2 page 193, Aaron erected the altar in order to hold on to it so that the people should not be able to drag him away from there and execute him. The Torah legislated that [normally, when the crime of the accused had not been murder, Ed] the altar serves as a refuge for someone who is guilty of legal execution. While the guilty person holds on to it the messengers of the court cannot violate the sanctity of the altar in order to carry out the court's verdict.

3חג לה׳ מחר, "To-morrow shall be a feast for the Lord." Aaron's intention was simply to stall the people and to gain time until Moses would return and control the situation. By using the Ineffable Name, Aaron had made it plain that he meant for the feast to be in honour of the One and Only G'd. He did not expect the Israelites to disagree as we pointed out already that no one had dared to deny the primacy of the G'd who had introduced Himself at the revelation at Mount Sinai as "I am the Lord Who has has taken you out of Egypt." All the people wanted was to take "part" of that G'd and look at it as a symbol of the invisible Lord in Heaven.