Sacrifices of Thanksgiving

What does God think of people who do external acts of piety but whose heart is not in the right place? In surprisingly clear language Psalm 50 describes God's sentiment towards those who do the workings of religion but disregard the true heart of worshiping God. This is a sobering message that calls all professing believers to worship the Lord with sacrifices of thanksgiving, and not be caught unaware of the dangers of an external religious facade.