How do we know God opens hearts in salvation?

The biblical account emphasizes that all who are saved experience God's initiative in salvation, as affirmed in Acts 16:14, where Lydia's heart was opened by the Lord. This is echoed throughout Scripture, such as in Psalms 110:3, which states, 'You make your people willing in the day of your power.' Thus, it illustrates that apart from divine intervention, no one can genuinely turn to God or understand His truth, underscoring the belief in God's sovereign grace in the process of salvation.