What was Jesus saying?

"And he said unto them, Go ye into all the world, and preach the gospel to every creature. He that believeth and is baptized shall be saved; but he that believeth not shall be damned." - Mark 16:15-16 KJV

He that believeth what?

The gospel!

What is the gospel?

Christ died for our sins, He was buried, He rose again the third day. (1 Corinthians 15:1-4)

If we are going to be saved, we must BELIEVE the gospel, AND be BAPTIZED.

When we are baptized, we have OBEYED the gospel. (Baptized of water and of the Spirit – John 3:5).

We “obey” His death by dying to sin by repentance.

We “obey” His burial by being buried with HIM by baptism in JESUS name.

We “obey” His resurrection by being filled with His Spirit so that we walk in new life. (Romans 6:1-4).

"But they have not all obeyed the gospel. For Esaias saith, Lord, who hath believed our report?" - Romans 10:16 KJV

"For the time is come that judgment must begin at the house of God: and if it first begin at us, what shall the end be of them that obey not the gospel of God?" - 1 Peter 4:17 KJV

"In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ:" - 2 Thessalonians 1:8 KJV

On the Day of Pentecost, after hearing Peter preach the gospel – the death, burial, and resurrection of Jesus – the people asked Peter and the rest of the apostles, “Men and brethren, what shall we DO?” (my emphasis).

"Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call." - Acts 2:38-39 KJV

Conclusion: Jesus is saying, he that believeth the gospel and is baptized shall be saved.