In discussions with Baptist preachers, you are apt to hear them say baptism is an "outward sign of an inward grace." They will affirm baptism is not essential to salvation, but claim it "declares our salvation." While this doctrine is not taught in the Bible (cf. Acts 22:16; 1 Peter 3:21), it is taught in Baptist manuals.
"Through the symbolic act of baptism, an individual states that he has turned from sin to Christ. By the act of public baptism, the new Christian demonstrates to the world that he has been redeemed and is now a new person in Christ." (Broadman Church Manual, p. 34).
"We do not believe that baptism is essential to the pardon of past sins, but believe that it is an act of righteous obedience to the command and example of our Lord, and that it serves as an open confession to the world that the subject has put away sin and put on Christ." (Doctrines and Usages of General Baptists, p. 90).
I have often wondered how baptism could "declare our salvation to the world," since the "world" was not present when we were baptized. It seems to me Baptist baptism could only "declare salvation" to the members of the Baptist church who were present. But, the members of the church already knew about the candidates "salvation" when they sat in judgement like a coroners inquest and voted on whether to receive him.
If baptism does not "declare our salvation to the world," what does? I would suggest it is the new life effected by repentance. When Peter told his audience to "repent and be baptized" (Acts 2:38), how many people "of the world" witnessed the baptism of the 3,000? Some of those baptized that day were far away from home (Acts 2:9-11). Their neighbors were not present at Jerusalem. However, when these new Christians returned home, the "world" would be able to see their new life (Romans 6:4).
Repentance is often described as a change of heart that brings about a change in action. It is not simply sorrow for sin. The people in Acts two were filled with sorrow and regret when they learned they had crucified the Son of God. Yet, Peter told these people to "repent and be baptized" (Acts 2:38).
The parable of the two sons (Matt. 21:28-32) is a good example of repentance. The young boy heard his father's command, but refused to obey. Later, he repented and did the will of his father. There could never be a question about his repentance, for he left his place of rest and went into his father's vineyard.
The prodigal son is another example of genuine repentance (Luke 15:11-24). After he left his father's house, he journeyed into a far country and there wasted his money in prodigal living. His older brother knew the young man had spent his inheritance on the harlots (vs. 30). When the prodigal's money ran out, he found a job feeding carob pods to the swine. While in the pig pen he "came to himself." He decided to arise, go to his father and admit his sin. I'm sure his neighbors knew how he wasted his money in a foreign land. Now they would see the change in his life (repentance).
When the Scribes and Pharisees tested Jesus in Matthew 12:38-42, He said "The men of Nineveh will rise in the judgement with this generation and condemn it, because they repented at the preaching of Jonah; and indeed a greater than Jonah is here." The story of the Ninevites is the greatest story of repentance in the Old Testament. Jonah was sent to this great city and told to preach to it (Jonah 3:2). As he preached, "the people of Nineveh believed God, and put on sackcloth, from the greatest to the least of them" (Jonah 3:5). Even the king repented, and published a decree demanding that "everyone turn from his evil way and from the violence that is in his hands" (Jonah 3:8). "Then God saw their works, that they turned from their evil way; and God relented from the disaster that He had said He would bring upon them, and He did not do it" (Jonah 3:10). Their change of heart brought about a change of action.
The repentance at Nineveh could be summed up with the words of Isaiah , "Let the wicked forsake his way, and the unrighteous man his thoughts; let his return to the Lord, and He will have mercy on him; and to our God, for he will abundantly pardon" (Isaiah 55:7).
Repentance carries with it evidences which the world cannot question. The residents of Ephesus could never doubt the sincerity of those converted in their city. As Luke records the salvation of these people, he said "many of those who had practiced magic brought their books together and burned them in the sight of all. And they counted up the value of them, and it totaled fifty thousand pieces of silver" (Acts 19:18-19).
The Philippian jailer gave evidence of his repentance when he washed the stripes of Paul and Silas, accepted the word of God, and set food before them (Acts 16:33, 34).
Under the Mosaic Law, God demanded restitution. "When a man or woman commits any sin that men commit in unfaithfulness against the Lord, and that person is guilty, then he shall confess the sin which he has done. He shall make restitution for his trespass in full value plus one-fifth of it, and give it to the one he has wronged" (Num. 5:6,7; cf. Lev. 6:1-7). While this law is not repeated in the New Covenant, another passage leads you to the same conclusion. Jesus said, "Whatever you want men to do to you, do also to them" (Matthew 7:12). If I expect restitution from those who have wronged me, I must practise it myself.