God doesn't sneak judgment in on us-He doesn't play games or try to trick us. He repeatedly tells us that if we ignore His Word and choose sin that destruction will follow. We establish a pattern of ignoring His warnings and then are devastated when the consequences fall on us.
In the book of Joel, the prophet is revealing a message from God concerning the destruction that is on the way. The Israelites have forsaken God for too long and are about to suffer the consequences. Staying true to His compassionate nature, God again offers an opportunity at repentance in Joel 2:12-14. He tells them to return to Him, but to "rend their hearts and not their garments."
It was a cultural sign of sorrow to tear your clothing and it symbolized the remorse that you felt over your current circumstances. It was supposed to be a reflection of the deep anguish that was felt over sinning against God, but easily turned into a false display of humility and repentance that did nothing to bring about transformation. While we no longer tear our clothes, this disingenuous action is still seen in dashing to the altar at the end of the service for prayer while doing nothing all week to actually change our hearts.
God's greatest desire isn't for us to do the right thing externally. It is for our hearts to truly be broken over our sin against Him and for that soul transformation to be reflected in the decisions we make. Authentic pursuit of godly repentance is the key to personal and community revival.