Literally, Micah’s mother starts out by saying, I solemnly consecrate the silver to the Lord.
So far, so good; this leads us to expect a positive outcome to the story, since she wants to consecrate the tainted silver for divine use.1 But this is followed by her indicating what she is solemnly consecrating: she plans to honour the Lord by using the money for making a carved image and a metal image.
In other words, for the purpose of idolatry! She will dedicate the silver to the honour, the glory of God.2 She wants these carved and metal images to be used in the worship of the Lord! This is a direct violation of the second commandment. It would be funny if it were not so terrible.
She is worshipping the Lord according to her wisdom instead of the Lord’s decrees. But she has got no idea! Her lack of knowledge of the basic laws of God shows how sinful the nation really was. To be sure, her heart is in the right place. She wanted to honour the Lord! But that does not at all justify what she did. The Lord definitely wants your heart in the right place when you worship. But he also wants you to worship in the way he specifies. This is lost on Micah’s mother. And she ends up bringing on herself the curse from Deuteronomy 27:15: Cursed be the man who makes a carved or cast metal image, an abomination to the Lord.
Her worship is impure.
3 And he restored the 1,100 pieces of silver to his mother. And his mother said, “I dedicate the silver to the LORD from my hand for my son, to make a carved image and a metal image. Now therefore I will restore it to you.”