Many who consider the meaning of this verse reflect on the miracles that Jesus performed —raising the dead, walking on water, and feeding thousands and consider these the "works" referred to in this context. The Greek word for Works used here is #2041, Ergon and it means: action, labor, deed that completes an inner desire (intention, purpose)
This is the same Greek word used in Matthew 11:2-5 "When John, who was in prison, heard about the deeds (#2041, works, ergon) of the Messiah, he sent his disciples to ask Him, "Are you the one who is to come, or should we expect someone else?" Jesus replied, "Go back and report to John what you hear and see. The blind receive sight, the lame walk, those who have leprosy are cleansed, the deaf hear, the dead are raised, and the good news is proclaimed to the poor."
Luke 24:19 "What things?" he asked. "About Jesus of Nazareth," they replied. "He was a prophet, powerful (#1415. dunatos) in word and deed (#2041, ergon) before God and all the people."
John 5:36 "I have testimony weightier than that of John. For the works (#2041, ergon) that the Father has given me to finish--the very works (#2041, ergon) that I am doing--testify that the Father has sent me."
So the works of Jesus certainly does include miracles ranging from giving sight to the blind and proclaiming the good news (the gospel, #2097 euangelizontai). Both powerful in "word and deed". The Greek word for powerful is Strongs #1415, dunatos, and is describing what is made possible because of the power (ability) exerted by the subject; "preeminent ability or power in something"
But this word "ergon" is also used in other verses such as Matthew 23:3 referring to the pharisees and says "[So be careful to do] Therefore, all that they tell you, do and observe, but do not do according to their deeds (#2041, ergon); for they say things and do not do them."
Mark 13:34 "It's like a man going away: He leaves his house and puts his servants in charge, each with their assigned task (#2041, ergon), and tells the one at the door to keep watch."
John 3:19 "This is the verdict: Light has come into the world, but people loved darkness instead of light because their deeds (#2041, ergon) were evil."
So "works" can refer to tasks and deeds and I would say represents the fruit of a person and is reflective of their inner man.
Philippians 1:6 "For I am confident of this very thing, that He who began a good work (#2041, ergon) in you will perfect it until the day of Christ Jesus."
John 3:21 ""But he who practices the truth comes to the Light, so that his deeds (#2041, ergon) may be manifested as having been wrought in God."
What works should we be doing
John 6:27-29 Do not work (#2038b from #2041, ergon) for food that perishes, but for food that endures to eternal life, which the Son of Man will give you. For on Him God the Father has placed His seal of approval.” Then they inquired,“What must we do to perform the works (#2041, ergon) ( of God?” Jesus replied, “The work (#2041, ergon) of God is this: to believe in the One He has sent.”
Ephesians 2:10 "For we are God's handiwork, created in Christ Jesus to do good works (#2041, ergon), which God prepared in advance for us to do."
James 2:17 "Even so faith, if it has no works (#2041, ergon), is dead, being by itself."
What does it mean that those who have faith in Him will perform “even greater” works than Christ?
Jesus said that not only would His followers do the same works, but they would do “greater” works than He.
The Greek work for greater is #3173, meizona and it means great in the widest sense, all the more, larger, wide.
Again, this is not a reference to the works’ being greater in power....for our power comes from Christ. No one has ever exceeded the power or majesty of Jesus’ miracles.
"Therefore, my dear friends, as you have always obeyed - no only in my presence, but how much more in my absence - continue to work (#2716,katergazomai) out your salvation with fear and trembling. for it is God who works (#1754, energeó) in you, both to will and to work (#1754, energeó) for His good pleasure." Philippians 2:12-13
[Note: #1754, energeo is formed from #1722/en "engaged in" which intensifies and #2041/ergon "work" and properly means energize, working in a situation which brings it from one stage (point) to the next, like an electrical current energizing a wire, bringing it to a shingling light bulb]
So, what did Jesus mean that His faithful followers would do “greater” works than He? Without a doubt, the works of Jesus’ followers would be greater in extent. Jesus’ earthly ministry had been largely limited to Galilee and Judea; His disciples, however, were going to extend His ministry to the uttermost parts of the earth. When Jesus ascended to heaven, His followers numbered in the hundreds; forty days later, in response to the preaching of the apostles, that number leaped into the thousands (Acts 2:41). By the end of Acts, the gospel had made its way to Rome.
Jesus said, “Whoever believes in me will do the works I have been doing, and they will do even greater (#3173, meizona) things than these, because I am going to the Father” (John 14:12).
Jesus links the works of His followers with the fact of His return to heaven. In fact, He says His absence is the cause of their greater works (#2041, ergon). Jesus later told His disciples that the gift of the Holy Spirit depended on Jesus’ return to heaven (John 16:7). It was through the Spirit that the church is enabled to do the work of God.
Jesus also links the greater works His followers will do to the promise of answered prayer. His very next words: “And I will do whatever you ask in my name, so that the Father may be glorified in the Son. You may ask me for anything in my name, and I will do it” (John 14:13–14).
The words of Jesus in John 14 were of great comfort to His eleven disciples. He was about to be arrested and suffer a cruel and unjust death. The disciples themselves would be scattered that night. But Jesus assures them that, no matter what happens, God’s work will continue in the world. Even after Jesus’ earthly ministry ended, His work would go on. The followers of Christ, empowered by the Holy Spirit, would continue to help and heal people. The gospel would have a worldwide impact. As God’s people pray in Jesus’ name, answers would come, and the greatest miracle of all—the spiritual transformation of a sinful heart through faith in Christ—would become commonplace, to the glory of God.
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Romans 1:16 tells us that the gospel (#2098, euangelion) is the power of God for salvation for everyone who believes).
Ref: Got Questions sourced from Jesus: The Greatest Life of All by Charles Swindoll