How do we know Jesus' prayer for forgiveness is effective?

The effectiveness of Jesus' prayer for forgiveness is illustrated by the immediate outcomes witnessed during His crucifixion. First, one of the criminals crucified alongside Him expressed faith in Jesus, asking Him to remember him when He came into His kingdom, to which Jesus replied, 'Today, you will be with me in Paradise' (Luke 23:43). This response exemplifies the power of Christ's intercessory prayer. Secondly, after Jesus' death, a centurion exclaimed, 'Truly this was the Son of God,' acknowledging the righteousness of Jesus (Matthew 27:54). These moments serve as testament to the transformative power of Christ's prayer, alongside the later events of Pentecost where thousands came to faith, indicating that His intercession indeed reached those for whom He prayed.