Some may ask what has obedience got to do with what Jesus did on Calvary? After all, was what He did at Calvary sufficient for whoever would accept His sacrifice for sins? On the other hand there are probably those who think that what we do activates the salvation of God in our lives. But what does the Bible say? In 2nd Thessalonians 1:7-9 Apostle Paul said, "And to you who are troubled rest with us, when the Lord Jesus shall be revealed from heaven with his mighty angels, In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ: Who shall be punished with everlasting destruction from the presence of the Lord, and from the glory of his power..." Apostle Peter also asked a couple of rhetorical questions about obedience to the gospel when he said in 1st Peter 4:17-18, "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? And if the righteous scarcely be saved, where shall the ungodly and the sinner appear?" It seems pretty clear to me that obedience to the gospel is rather important.
So what is obedience to the gospel? Apostle Paul gave a definition of the gospel in 1st Corinthians 15:1-4 where he said, "Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand; By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain. For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures..." In a nutshell the gospel is the death, burial and resurrection of the Lord Jesus for your and my sins, as long as we believe. The question is, why would Jesus willingly lay down His life for you and I? Jesus said in John 15:13, "Greater love hath no man than this, that a man lay down his life for his friends." It was because He loved you and I that He gave His life for us.
So the question is asked again, what is obedience to the gospel? This is not rocket science! Neither is it juggling or replacing the scriptures to suit oneself. Just the simple teaching of the Bible. Jesus told Nicodemus in John 3:5, "Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God." Neither you nor I can expect to be saved without the born again experience. Being born again of the water and the Spirit is not optional. Jesus said in John 3:7, "Marvel not that I said unto thee, Ye must be born again." What is being born of the water and Spirit? On the day of Pentecost after Apostle Peter preached the first Christian message to his Jewish listeners. They, recognizing that they had indeed crucified their Messiah whom God had sent to be their Saviour said, "Men and brethren, what shall we 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. 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." (See Acts 2:37-39)
My friend whoever you are, what Jesus said to Nicodemus is still applicable today. Being born again is much more than just a good feeling one may get when they acknowledge that what the Lord Jesus did at Calvary was for them and accept Him as their Saviour. If one truly turns from their sin at that time it is called repentance. Obedience to the gospel is repentance from the way you have always lived, baptism in water in Jesus saving name for the forgiveness or remission of sin and receiving the promise of the Father, the Holy Spirit or Holy Ghost, with the evidence of speaking in a new language, just as the apostles and the early church did on the day of Pentecost. If you have not done these things, you have not obeyed the gospel. In our first reading in 2nd Thessalonians 1:7-9 the Bible says that the Lord Jesus is coming back and that He will take vengeance on those who refuse to know God and who have not obeyed the gospel. In 2nd Thessalonians 1:10 the Bible says He will come back "to be glorified in his saints, and to be admired in all them that believe (because our testimony among you was believed) in that day."
Another old song comes to mind, the chorus which goes as follows:
Are you ready, are you ready,
Are you ready for the judgment day.
Are you ready, are you ready,
For the judgment day.