Aaron helped the people mold a golden calf for them to worship, since they insisted on something visible to bow down to. When Moses returned, Aaron said they had only thrown the gold in the fire, and the golden calf miraculously formed.  We want our idols to be miracles of themselves, but they are always only made by human hands.  Aaron, God's priest, joined in the rebellion against God.  Stephen was pointing out that even those who are supposed to represent God can be working against Him. He was speaking to the religious leaders at this time, and he told them that they weren't the first religious leaders to be wrong.  God had provided a tabernacle for the people, but they wanted something more.  Stephen recounted how much later, after the people were established in the Promised Land that David wanted to build temple to God.  The building of the temple actually occurred when Solomon was king, but even then God reminded His people that He did not reside in temples made by hand. Yet, the temple had become more important to the religious leaders than the God it was built to worship.  God doesn't dwell in temples, or church buildings, but in the hearts of His people.  When people are not in the church building, it is just a building, but when two or three are gathered in His name, it becomes a house of worship.  We must never let the building become more important than the God that it represents or it can become our golden calf.