Truly, truly, I say to you, he who believes in Me, the works that I do, he will do also; and greater works than these he will do; because I go to the Father.
John 14:12 (NASB)
Jesus promised His disciples that they would do "greater works" after He returned to the Father. In the context of the verse, he was describing how God would use them to spread the gospel from a small part of the world to all four corners of the earth. On the day of Pentecost, Jesus fulfilled His promise by sending the Holy Spirit to empower them (and us) to witness and testify confidently.
We must not assume that "greater works" imply superior revelational knowledge or healing power compared to Jesus. Rather, the Greek word for "greater works" is meizon, which means "more extensive or greater influence". In other words, Jesus is stating that we, as His Church, will touch more lives and impact more communities than He could ever do while on earth.
In history, the Church has repeatedly discovered the power of doing "greater works" in Jesus' name. I believe that every believer has the supernatural ability to witness for Christ and make disciples. Many of us believe that soul winning is difficult work. This is because we are depending on our own strength instead of depending on the Holy Spirit to convict the hearts of people.
Jesus refers to the Holy Spirit as our Helper (John 14:16), and as such, we must learn to work with Him and bring people into salvation. This laid the groundwork for the early church's success in spreading the gospel. Thus, ask the Holy Spirit to provide you with an opportunity to share the gospel with someone, and be amazed at what He can accomplish through you.