How do we know God's mercy is specific to the elect?

God's sovereignty in bestowing mercy is a foundational tenet of Reformed theology. Romans 9:15 clearly declares that God exercises His mercy according to His divine will, implying it is not offered universally to all but specifically to the elect. The implication here is profound; those who need mercy must recognize their sinful condition and turn to God, as seen in Mark 2:17. The awareness of one's need for mercy is an indicator of being chosen by God, as He works within His elect to bring them to faith in Christ, who fulfilled the requirements for atonement through His death and resurrection. This sovereignty assures believers that their salvation is secured by God's grace alone, and not by any merit of their own.