2. When the jailer in Acts 16:31 asked how to be saved, Paul and Silas told him that all he had to do was believe.
Not exactly. The jailer did ask Paul and Silas, “Sirs, what must I do to be saved?” And they did tell him, “Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house.” But “shalt be” is future indicative and implies a future time, not automatically, right now with nothing else involved. Moreover, if we stop here, then everyone in the jailer’s house would be saved because the jailer believed. Just consider the very next verse (32) : “And they spake unto him the word of the Lord, and to all that were in his house.” Faith (saving faith) cometh by hearing, and hearing by the Word of God. In other words, they went home with the jailer and preached the gospel to him and his household. What did Paul and Silas preach to these folks? We are not given a single word, but the people went out sometime after midnight, in the company of the prisoners, to be baptized “straightway.” Back at the jail, the jailer would have committed suicide for fear of the Roman soldiers, but after Paul and Silas gave him the Word of the Lord, baptism became more important than his very life.
Would anyone go out in the middle of the night (at risk) to be baptized, if it were not essential? Baptism is exactly how Paul had his sins washed away, so it’s doubtful he would tell these folks that they could be saved without being baptized. Jesus expressed an opinion on the subject: “He that believeth and is baptized shall be saved.” ( Mark 16:16).
Paul also wrote that without the Spirit of Christ, we are none of his. While the main focus of this account is on water baptism, the jailer would have needed to receive the Spirit as well. We can turn to Acts 19 and see a detailed example of Paul’s ministry, including the people’s response and a written record of what happened when someone received the Holy Ghost under Paul’s preaching.
Further, all the apostles preached the same gospel. Jude, in his letter, refers to the “common salvation” and admonishes us to “Contend for the faith that was once delivered unto the saints.” What does contend for mean? It means to fight for, to defend. What faith was once delivered unto the saints? The one that began at Jerusalem on the Day of Pentecost.
Indeed, Galatians 1:23 says of Paul: “That he which persecuted us in times past now preacheth the faith which once he destroyed.” What faith had Paul destroyed? The one that began in Acts 2.