Though Ephraim built many altars for sin offerings, these have become altars for sinning (Hosea 8:11 NIV).
God is here giving us a solemn warning. It points out great pretensions that can happen in our spiritual life. God had given the Israelite people the ability to build a temple for His name. They were asked to offer their sacrifices there. When time passed, the people began to forsake God and His temple. Then they started to build many altars for sin offerings at many places.
At first look, this practice might seem to be a sign of great devotion to God. Yet in fact, it was great violation of His commands. In the first place, they were disobeying God’s command of bringing their sacrifices to the temple of God and worshipping God there. Secondly, they were imitating the vile and detestable practices of their neighbors who sacrificed to other gods in the altars they had everywhere. This God had forbidden.
So we find here that the very building of altars that should have been a sign of great spirituality actually had become a sign of rebellion against God. We should therefore be careful how we worship God. It is easy for what we think to be some great spiritual act of worship to degenerate into something sinful.
There is another solemn thought that occurs here. These altars were meant for sin offerings which was an act of worship meant to cover the sins of people before God through the blood of the sacrificed animal. Yet instead of this noble purpose we find that these altars became altars for sinning. In Christian life too, if we are not careful, the best can easily become the worst; and the good, evil!