The excitement of Easter was in checking if the people have seen Jesus. The chronological privilege on the resurrection day belongs to the women at the tomb, the two disciples on the way to Emmaus and to the ten apostles in the evening. Mary Magdalene runs to the disciples and tells them "I have seen the Lord!"(John 20: 18). The two disciples who had dinner with Jesus leave Emmaus immediately and return to Jerusalem, telling the apostles how they have recognized him when he broke the bread at the table (Luke 24:28). The disciples tell Thomas, "We have seen the Lord!" (John 20:24).
The importance of seeing the Lord is demonstrated when the apostles are choosing a disciple to replace Judas who has betrayed Christ. One of the qualifications was to have been a disciple and the other is to have seen the Lord Jesus before he was taken into heaven. (Acts 1:21-22). The apostle Paul writes that Jesus Christ was seen by more than 500 brothers at the same time and the majority of them were still living in his time. (1 Cor. 15:3-8).
Why this meticulous emphasis on seeing the Risen Lord? The answer is given by Jesus Christ and by the beloved disciple at the conclusion of his gospel and the beginning of his epistle.
Jesus tells Thomas, "Because you have seen me, you have believed: blessed are those who have not seen and believed." The stage is set. It was important for the apostles to have the experience of seeing Jesus Christ. It was important for a large group - over 500 people - to see Jesus. The resurrection of Jesus was attested to by those who were eyewitnesses of the Risen Lord. However, the time of sightings was short - 40 days. After 40 days Jesus ascended to heaven and seeing him was a rare exception. Only Stephen saw him at his death.
From the Day of Ascension until now, we believe the witnesses that have written to us about the risen Lord. John concludes the twentieth chapter of his gospel: Jesus did many other miraculous signs in the presence of his disciples, which are not recorded in this book. But these are written that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name. (John 20:30-31).
He begins his epistle with a slightly modified introduction. "That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked at and our hands have touched - this we proclaim concerning the Word of life. The life appeared; we have seen it and testify to it, and we proclaim to you the eternal life, which was with the Father and has appeared to us. We proclaim to you what we have seen and heard, so that you also may have fellowship with us. And our fellowship is with the Father and with his Son, Jesus Christ. We write this to make our joy complete. (1 John 1:1-4)
The confirmation of the Risen Lord is attested in two ways - the testimonies of the people that have seen Jesus Christ and the presence of the Holy Spirit in our lives. Paul writes: He who has the Holy Spirit has Christ. (Romans 8:9b) God the Father sent the Holy Spirit to confirm the resurrection of Jesus and to glorify Him for the work that he has done.
I can sing "He lives within my heart," not strictly because I am trusting my heart but because I am trusting the hundreds of eye witnesses and I am trusting the Holy Spirit.