How do we know that God's call to salvation is effective?

In Acts 16, we observe the effectiveness of God's call to salvation through the conversions of both Lydia and the jailer. Lydia's heart was opened to embrace the message Paul preached, leading her and her household to baptism (Acts 16:15). Similarly, the jailer, after a dramatic intervention, asked what he must do to be saved and believed, resulting in his baptism (Acts 16:33-34). These accounts illustrate the reality that God’s call is not merely an invitation but an effective summons that results in genuine faith and obedience. This underscores the sovereignty of God in salvation, affirming the belief that He actively draws individuals to Himself through His Word.