The Mekhilta constructs a powerful a fortiori argument about God's mercy. Within the framework of God's lesser measure — the measure of punishment — even a single individual who cries out against the many is heard. The Torah's doubling of "hear will I hear" (Exodus 22:22) establishes that God responds to the cry of any afflicted person, even one person wronged by an entire community.
If this is true for punishment — the lesser measure — then how much more must it be true for mercy — the greater measure! If the many pray on behalf of a single individual, God will certainly hear their prayer with even greater speed and attentiveness.
The underlying theology is that God's mercy always exceeds His punishment. The measure of divine compassion is always greater than the measure of divine justice. If justice responds to one person's cry against the many, mercy must respond to the many crying out for one.
This teaching had profound implications for the Jewish understanding of communal prayer. When a community gathers to pray for a sick person, a person in trouble, or someone facing judgment, their collective voice carries extraordinary power. The Mekhilta is saying that communal intercession is not merely a nice custom — it is a form of prayer that God has bound Himself to answer. The many praying for the one activates the divine measure of mercy, which is always ready to exceed what strict justice would require.