How do we know salvation is by God's strength?

The strength by which God saves us is His inherent holiness and justice. In Psalm 54:1, David appeals for God to save him 'by thy name' and 'judge me by thy strength,' highlighting the dual nature of God as a savior and a just judge. Throughout Scripture, it is emphasized that no one can save themselves; it is only through God's sovereign power that individuals are brought to faith and ultimately saved. This underscores the importance of God's strength and justice in the process of salvation, making it clear that it is not a matter of human effort or merit.