It was a breach of the second—
"Thou shalt not make unto thee any graven image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth: thou shalt not bow down thyself to them nor serve them."
The Israelites did not conceive that they were abandoning the worship of Jehovah; they still considered themselves as worshipping the one true God. They were monotheists still, not polytheists. But they had taken the first false step that inevitably leads to polytheism; they had forgotten that they had seen "no manner of similitude on the day that the Lord spake unto" them "in Horeb out of the midst of the fire," and they had worshipped this golden calf as the similitude of God; they had "changed their glory into the similitude of an ox that eateth grass." And that was treason against Him; therefore St. Stephen said, "God turned, and gave them up to worship the host of heaven;" the one sin inevitably led to the other, indeed, involved it. In a later day, when Jeroboam, who had been appointed by Solomon ruler over all the charge of the house of Joseph, led the rebellion of the ten tribes against Rehoboam, king of Judah, he set up golden calves at Dan and Bethel, and said unto his people, "It is too much for you to go up to Jerusalem: behold thy gods, O Israel, which brought thee up out of the land of Egypt." There can be little doubt that, in this case, Jeroboam was not so much recalling the transgression in the wilderness—it was not an encouraging precedent—as he was adopting the well-known cognizance of the tribe of Joseph, that is to say, of the two tribes of Ephraim and Manasseh, which together made up the more important part of his kingdom, as the symbol of the presence of Jehovah.
The southern kingdom would naturally adopt the device of its predominant tribe, Judah, and it was as the undoubted cognizance of the kingdom of Judah that our Richard I., the Crusader, placed the Lion on his shield.
More definitely still, we find this one of the cherubic forms applied to set forth Christ Himself, as "The Root of David," Prince of the house of Judah—
"Behold, the Lion of the tribe of Juda, the Root of David, hath prevailed to open the book, and to loose the seven seals thereof."
FOOTNOTES:
[187:1] Josephus, Antiquities of the Jews, III. vii. 5-7.