In verse 1, God through the prophet addresses the religious and political leaders of Israel as well the people in general. The reference to Mizpah (near the southern border) and Tabor (in the north) may be because idols had been placed there. Some scholars think the reference to slaughter concerns the brutality shown by those who tried to become king after the death of Jeroboam (mentioned in 1:1); others say it refers to child sacrifice that occurred at pagan shrines. Whenever it was and whoever was involved, the Lord was determined to punish them (v. 2).
The problem with Israel was her determination to continue with idolatry. Participating in idolatry was an expression of pride, a statement that they did not want the Lord’s help (v.5). (This spirit of self-confidence was also beginning to mark Judah.) Yet they retained an outward form of worship and attended religious occasions at the false shrines set up in the northern kingdom (v. 6). Those occasions looked very grand, with all their rituals, but they would not result in fellowship with God. Their religion was in reality an expression of the absence of contact between them and the God who had been so good to them.
Instead of living with God as their Husband, Israel had committed spiritual adultery with false gods. Her ongoing unfaithfulness had resulted in children who did not acknowledge the Lord. Subsequent generations no longer served him. But their participation in false worship (the new moon was when religious events occurred) would eventually devour them and cause them to lose their fields (v. 7).
There are two deductions from this passage that we can think about. The first is that it only takes one generation to depart from God and the outcome will be total ignorance of him in the next generation. The second is that humans remain religious even after they no longer worship the living God. So it is possible for complete ignorance of God and large religious practices to occur simultaneously.
The main message for us from this passage is that we should remain loyal to God. We are not his because we are descended from those who experienced his marvellous deliverance at the Exodus. Instead we are his because of what he did for us at the Cross when Jesus paid the penalty for our sins. We have far greater reasons for remaining loyal to him, but failure to be loyal may have greater consequences for us than it did for them.