The text of John 14:12 makes an important distinction between two types of works that Jesus does:
- The works that Jesus had been doing during His earthly ministry. This included things like (according Jesus' own declaration) "to preach good news to the poor, to proclaim liberty to the captives, and recovery of sight to the blind, to release the oppressed, to proclaim the year of the Lord’s favor." (Luke 4:18, 19). Thus, Jesus was preaching the good news, healing the sick and preparing people for the Kingdom of God.
- What Jesus would do when He returned to the Father (Matt 26:64, 27:38, Mark 14:62, 16:19, Luke 23:33, Acts 7:55, 56, Rom 8:34, Col 3:1, Heb 1:3, 10:12, 1 Peter 3:22, etc).
Note that Jesus is actually saying that the disciples would be doing greater works than they had seen Jesus doing, that is, type #1 works above. Jesus works in heaven (#2 above) were to enable the disciples to do the type #1 works.
Ellicott correctly observes:
He that believeth on me, the works that I do shall he do also.--He
that by faith becomes one with the Son shall have the Son, and
therefore also the Father, dwelling in him (John 14:11; John 14:20;
John 14:23), and shall himself become an instrument through which God,
who dwelleth in him, shall carry into effect His own works. He shall,
therefore, do works of the same kind as those which the Son Himself
doeth.
And greater works than these shall he do.--Comp. Notes on John 5:20,
and on Matthew 21:21-22. The explanation of these greater works is not
to be sought in the individual instances of miraculous power exercised
by the apostles, but in the whole work of the Church. The Day of
Pentecost witnessed the first fulfilment of this prophecy; but it has
been fulfilled also in every great moral and spiritual victory. Every
revival of a truly religious spirit has been an instance of it; every
mission-field has been a witness to it. In every child of man brought
to see the Father, and know the Father's love as revealed in Jesus
Christ, has been a work such as He did. In the world-wide extent of
Christianity there is a work greater even than any which He Himself
did in the flesh. He left His kingdom as one of the smallest of the
influences on the earth; but it has grown up as a mighty power over
all the kingdoms of the world, and all that is purest and best in
civilisation and culture has found shelter in its branches.
Because I go unto my Father.--The better reading is, because I go unto
the Father. The words are to be connected not with one clause only,
but with all the earlier parts of the verse. They are the reason why
the believer shall do the works that Christ does, as well as the
reason why he shall do greater works. The earthly work of Christ will
have ceased, and He will have gone to the Father. The believers will
be then His representatives on earth, as He will be their
representative in heaven. Therefore will they do His works, and the
works shall be greater because He will be at the Father's right hand,
and will do whatsoever they shall ask in His name.
So, did the disciples do "greater works" that Jesus? In some respects they did. Here are a few examples:
- Peter preached a sermon (Acts 2) that resulted in the baptism of 3000 people. (Jesus never had that sort of success)
- Peter was also the first to preach the good news to gentiles (Acts 10) and baptised a gentile family
- Paul travelled widely and was probably responsible for thousands of conversions to Jesus (via the work of the Holy Spirit); far more than Jesus.
- Paul and other disciples established new Christian communities around the world which Jesus, while on earth, never did.
- Collectively, the disciples performed far more signs and wonders that Jesus could in the limited time He had during His earthly ministry (Acts 2:43, 4:30, 5:12, 6:8, 8:13, 14:3, 15:12, Rom 15:19, 2 Cor 12:12, Heb 2:4, etc.)
Thus, Jesus' prophecy in John 14:12 came true and is still being fulfilled to this day.