When Jesus was at leaving the earth, He left his disciples with a great commandment, a very simple one though:
Mark 16:15 And he said unto them, Go ye into all the world, and preach the gospel to every creature.
HOLD ON
the disciples did not just set-off right away to preaching this "GOSPEL". they had to wait on something.
Acts 1:7-8
[7] And he said unto them, It is not for you to know the times or the seasons, which the Father hath put in his own power.
[8] But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judæa, and in Samaria, and unto the uttermost part of the earth.
Shall be witnesses?
What did Jesus really mean by that statement?
A witness is one who has first account of an incident, either by seeing or hearing them happen
If there was anyone who could be a witness to the works of Jesus, it had to be The disciples, yet Jesus said they had to wait for the Holyghost to make them witnesses.
It means the Gospel that was to be preached was not what the disciples had in mind.
1st Corinthians 15:1-6
[1]Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;
[2] By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.
[3] For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
[4] And that he was buried, and that he rose again the third day according to the scriptures:
[5] And that he was seen of Cephas, then of the twelve:
[6] After that, he was seen of above five hundred brethren at once; of whom the greater part remain unto this present, but some are fallen asleep.
This is why Jesus told the disciples that they needed to Holyghost in order to be witnesses of the gospel, because the disciples didn't understand:
why he died
where he went after his death
what he did for man by his death
what happened at the Mercy seat of God etc
A messenger is always sent with a message and must not at anything add his words or feelings to the delivery of the message but must deliver it, the way it was told him.
The message of the gospel is a single topic, it fits whatever audience.
The message we have been sent to preach is Jesus, his death, his burial, his ressurection, his ascension, his coronation and THE BENEFIT IT AFFORDS THE BELIEVER
Jesus came to address a universal problem, which is highlighted in
Romans 3:23:
For all have sinned, and come short of the glory of God;