How do we know God's mercy is what makes us differ?

The doctrine of God's sovereignty in salvation is affirmed in Romans 9:15-16, which states, 'I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion.' This clearly asserts that it is not by our will or efforts that we receive variation in our spiritual condition but by divine mercy alone. Recognizing this truth humbles us, as it moves the focus away from our actions and onto God's gracious hand. Likewise, in 2 Timothy 1:9, we read about how He saves us according to His purpose and grace, showing that His mercy is the crucial factor in creating any distinction among people. Thus, it is God's unmerited favor that defines our differing positions before Him.