How can I explain verses like Matthew 16:28 where it seems like Jesus was
saying to some that they wouldn’t die before seeing the Son of man coming
in His Kingdom ? Jesus did not came back in the first century. Was he
saying that he would come back in the first century, or did he mean
something else?

Jesus did indeed come in his Kingdom during the lifetime of most of those
who heard him on that day. The subject of the Kingdom of God is a broad
and deep one. The Kingdom of God is in one sense the kingship of God in
any one individual’s life. It will also be revealed at the end of time
when the final Kingdom of God will be the eternal city–heaven.

All this is true, but in the context of Matthew 16:28, Jesus is talking
about the kingdom of God in the sense he most commonly uses it in the
gospels. One aspect of the kingdom of God is the church of Christ. The
church is the kingdom. In fact, Jesus had just finished making that point
in Matthew 16:17-19 where Jesus clearly equates the church with the
Kingdom of Heaven. Jesus appears to use the phrase Kingdom of God and
Kingdom of Heaven virtually interchangeable in the gospels.

So when was the prophecy fulfilled? The answer is that the Kingdom of God
and of the Son Jesus Christ came on the day of Pentecost, 50 days after
the resurrection of Jesus. This fulfillment is found in Acts chapter two.
Many prophecies, both in the Old Testament and the New Testament point to
the coming of the Kingdom in a new and unique way on the Day of Pentecost.
For example, one could look at Isaiah 2:2-4. Daniel 2:44,45, Matthew 3:2,
Luke 24:45-47, Matthew 16:18-20 and Matt 16:28 all point to the events of
the pouring out of the Spirit, the first public gospel sermon and the
first conversions to Christ which all occurred on the Day of Pentecost, as
recorded in Acts chapter two.

Jesus did not visibly, physically come back on the Day of Pentecost, but
he God certainly did come in the person of the Holy Spirit on that day.
There are many passages which express the thought that Jesus comes to us
when we receive the gift of the indwelling Holy Spirit. 1 Corinthians
15:24, John 14:15-21 and John 16:7-15 come to mind.

John Oakes, PhD