In Bible-believing churches, we use terms like sin and grace all the time. We think we know what they mean but have not begun to fathom their true depth and height. In Haggai 2, God shows us how bad our sin really is so that we might understand how amazing His grace really is, ultimately through the Savior who became defiled that we might be cleansed.
Like the good Father that He is, God disciplines and corrects us when we go astray. But He also empowers us when we are weak. After taking His people to the woodshed in chapter one, God strengthens and encourages them in chapter two by reminding them of His presence and His plan. He would remain with them in power and would use them to prepare the way for the ultimate Temple, who would secure their ultimate peace, Jesus Christ. God strengthens us through the same Savior as we continue His work today.