According to Romans 6:1-6 and 1 Corinthians 15:1-4, the gospel is the salvation message of how Christ lived, died on the cross, was buried, and rose again from the dead to take away our sins. These two passages also teach us to, in like manner, die to all sins, be buried in the waters of baptism, and raised to walk in the newness of life.
These are the gospel facts and are what we must do to be saved. (Acts 2:37-41 and Acts 8:26-40)
This is both our command and our example.
6 “What shall we say then? Are we to continue in sin so that grace may increase?2 May it never be! How shall we who died to sin still live in it? 3 Or do you not know that all of us who have been baptized into Christ Jesus have been baptized into His death? 4 Therefore we have been buried with Him through baptism into death, so that as Christ was raised from the dead through the glory of the Father, so we too might walk in newness of life. 5 For if we have become united with Him in the likeness of His death, certainly we shall also be in the likeness of His resurrection, 6 knowing this, that our old self was crucified with Him, in order that our body of sin might be done away with, so that we would no longer be slaves to sin;” (Romans 6:1-6 NASB)
15 “Now I make known to you, brethren, the gospel which I preached to you, which also you received, in which also you stand, 2 by which also you are saved, if you hold fast the word which I preached to you, unless you believed in vain.3 For I delivered to you as of first importance what I also received, that Christ died for our sins according to the Scriptures, 4 and that He was buried, and that He was raised on the third day according to the Scriptures,” (1 Corinthians 15:1-4 NASB)
37 “Now when they heard this, they were pierced to the heart, and said to Peter and the rest of the apostles, “Brethren, what shall we do?” 38 Peter said to them, “Repent, and each of you be baptized in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the Holy Spirit. 39 For the promise is for you and your children and for all who are far off, as many as the Lord our God will call to Himself.” 40 And with many other words he solemnly testified and kept on exhorting them, saying, “Be saved from this perverse generation!” 41 So then, those who had received his word were baptized; and that day there were added about three thousand souls.” (Acts 2:37-41 NASB)
26 “But an angel of the Lord spoke to Philip saying, “Get up and go south to the road that descends from Jerusalem to Gaza.” (This is a desert road.) 27 So he got up and went; and there was an Ethiopian eunuch, a court official of Candace, queen of the Ethiopians, who was in charge of all her treasure; and he had come to Jerusalem to worship, 28 and he was returning and sitting in his chariot, and was reading the prophet Isaiah. 29 Then the Spirit said to Philip, “Go up and join this chariot.” 30 Philip ran up and heard him reading Isaiah the prophet, and said, “Do you understand what you are reading?” 31 And he said, “Well, how could I, unless someone guides me?” And he invited Philip to come up and sit with him.32 Now the passage of Scripture which he was reading was this:
“He was led as a sheep to slaughter;
And as a lamb before its shearer is silent,
So He does not open His mouth.
33 “In humiliation His judgment was taken away;
Who will relate His generation?
For His life is removed from the earth.”
34 The eunuch answered Philip and said, “Please tell me, of whom does the prophet say this? Of himself or of someone else?” 35 Then Philip opened his mouth, and beginning from this Scripture he preached Jesus to him. 36 As they went along the road they came to some water; and the eunuch *said, “Look! Water! What prevents me from being baptized?” 37 [And Philip said, “If you believe with all your heart, you may.” And he answered and said, “I believe that Jesus Christ is the Son of God.”] 38 And he ordered the chariot to stop; and they both went down into the water, Philip as well as the eunuch, and he baptized him.39 When they came up out of the water, the Spirit of the Lord snatched Philip away; and the eunuch no longer saw him, but went on his way rejoicing. 40 But Philip found himself at Azotus, and as he passed through he kept preaching the gospel to all the cities until he came to Caesarea.” (Acts 8:26-40)