Faced with a devastating locust plague destroying the land, the natural human reaction is to fall into outward displays of mourning. Yet, true restoration requires a much deeper, internal shift rather than mere physical expressions of grief.
In times of severe distress, it was a common custom to tear one's clothing as a visible sign of sorrow [אבן עזרא, ביאור שטיינזלץ]. However, the primary approach among commentators is that the demand here is for genuine inner submission. God places no true value on the physical act of tearing clothes if it is not accompanied by internal change [רש"י, מצודת דוד, ביאור שטיינזלץ]. Instead, the concept of tearing the heart means to break it open, removing the emotional barriers that block a person from understanding the truth, and clearing away evil thoughts [אבן עזרא, מצודת ציון, רד"ק].
Others view this dynamic as a direct cause and effect: if the people break their hearts in sincere repentance, they will be spared the agony of ever needing to tear their garments over a physical disaster [רש"י, רד"ק]. Offering another perspective, [מלבי"ם] suggests that the focus of the people's grief is misplaced. The mourning should not be directed at the physical suffering brought upon the land, but rather at the sins themselves, as moral failures are ultimately far more harmful to a person than the resulting punishment.
This profound inner submission must lead the people to return to God [מצודת דוד], a return that should ideally be motivated by love [מלבי"ם]. The ultimate hope for the people rests entirely on God's character. He is gracious, compassionate, endlessly patient, and abundant in kindness. He is willing to reconsider and change His plans for destruction into intentions for good [רש"י, מצודת דוד, מצודת ציון, ביאור שטיינזלץ]. The commentators agree that it is God’s very nature to extend mercy and revoke harsh decrees for those who genuinely return to Him [רד"ק]. Even if the disaster has already begun to unfold in reality, sincere repentance carries the power to awaken His compassion and bring an end to the punishment [מלבי"ם].