“A soap manufacturer and a [preacher] were walking together down a street in a large city. The soap manufacturer casually said, ‘The Gospel you preach hasn’t done much good, has it? Just observe. There is still a lot of wickedness in the world, and a lot of wicked people, too!’ The [preacher] made no reply until they passed a dirty little child making mud pies in the gutter. Seizing the opportunity, the [preacher] said, ‘I see that soap hasn’t done much good in the world, for there is much dirt and many dirty people around.’ The soap manufacturer replied, ‘Oh, well, soap is only useful when it is applied.’ And the [preacher] said, ‘Exactly, so it is with the Gospel.’” — James S. Hewett, “Illustrations Unlimited,” p. 354.

Paul also told us that we are saved by the Gospel. He put it a different way in Romans 1:16: “For I am not ashamed of the Gospel of Christ, for it is the power of God unto salvation to everyone that believeth, to the Jew first, and also to the Greek.”
Seeing how important the Gospel is may help us to see just why Jesus desired that the Gospel be carried to all the world. “And Jesus came and spake unto them, saying, ‘All power is given unto me in heaven and in Earth. Go ye, therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost. Teaching them to observe all things whatsoever I have commanded you, and lo, I am with you always, even unto the end of the world. Amen’” (Matthew 28:18-20).
If we can get to heaven by obeying the Gospel, we must learn how to obey it. There are three things that are needed in order to obey the Gospel: knowledge, understanding and an obedient heart.
First of all, let’s look at knowledge, which is defined as awareness of facts, truths or principles. In order to gain knowledge about the Gospel of Christ, we must be taught about him and what he has done for us. Isaiah 53 shows us what Christ has done for us. From that, we know he gave himself to die for us.
Having knowledge about the Gospel is good, but something more is needed — understanding. You might think of it this way: When one of your teachers at school introduces you to a new subject, you have the facts about the subject, but not the understanding. To gain understanding, more study is needed. It is the same with obeying the Gospel. We must continue studying the Bible to find out how to obey the Gospel. In the book of Acts, we have several accounts of how people did just that. Acts 2 tells us of how Peter preached to the multitudes in Jerusalem on day of Pentecost about the “good news” of Jesus. By his teaching, they received knowledge about Jesus and their need for him. Verse 37 tells us that they wanted to know what to do. “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’” (verse 38).
So we see they had knowledge and understanding, but one more thing was needed — an obedient heart. Luke tells us that about 3,000 had such hearts and were willing to obey the Gospel in order to be saved.
What happens when we are baptized? Physically, we are immersed in water. Paul described this process in Roman 6:3-5. “Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? Therefore, we are buried with him by baptism into death, that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life. For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection.” Spiritually, our sins are forgiven (Ephesians 1:7). We receive the remission of our sins (Acts 2:38). Are sins are washed away (Acts 22:16). And we are added to the church (Acts 2:47).
God loves all mankind, but man must accept that love and obey as God commands.