1)
The previous verse already said that they came to My Mikdash on the same day that they offered their children!
1.
Radak: The matter is repeated in different words.
2.
Malbim: Here it teaches that since they came to My Mikdash that same day, it is as if they slaughtered their children to idolatry in My house. This is like a wife who is Mezanah under her husband in his house, in front of him; she does not guard from him any more. This arouses the greatest Kin'ah!
2)
What do we learn from "Cho Asu b'Soch Beisi"?
1.
Radak: They did this profaning in My house. They drew images in the chambers of the Azarah and burned offerings to them.
2.
Malbim: Refer to 23:39:1:2.
