Acts 2:41 Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls.
You are right in concluding that there is not much in the way of a positive command telling us that baptism is a requirement for church membership. I believe that the verse above connects the two, but I will admit that it is not a direct command. Acts 2:47 further states, "And the Lord added to the church daily such as should be saved." Here baptism is not specifically in context and, even then, some think this is referring to a universal church and not the local church at Jerusalem.
With only one verse making a direct connection between baptism and church membership, with the meaning of that verse contested, with another verse that seems to make salvation the only necessity for church membership, and with practically every word and concept in the first few chapters of Acts being fought over today, it is no surprise that many are giving up on the requirement of baptism for church membership. We have a growing move away from any real qualifications for church membership other than salvation and a stated desire to be a member. In fact, more and more people are seeing no reason to join a church--even if they have been attending for a long time. The whole concept of church membership has been assigned a low value in the world of Christianity.
So, is there an answer? I believe there is. However, I believe we can settle the questions raised at the front door by studying the back door. That is, if we determine what excludes people from being part of a New Testament church, we may have a better idea as to what qualifies them to be included in membership. The key to what gets you in may be an understanding of what gets you out. I am talking here about church discipline.
Church discipline is not possible without some form of church membership. I am sure that the ancient church did not do things exactly as we do. However, they must have had a form of church membership. You cannot put someone out of the church unless there is a formal way in which they are accepted into the church. Here are some of the verses in the Bible that deal with church discipline:
Matthew 18:17 And if he shall neglect to hear them, tell it unto the church: but if he neglect to hear the church, let him be unto thee as an heathen man and a publican.
Romans 16:17 Now I beseech you, brethren, mark them which cause divisions and offences contrary to the doctrine which ye have learned; and avoid them.
1Corinthians 5:11 But now I have written unto you not to keep company, if any man that is called a brother be a fornicator, or covetous, or an idolater, or a railer, or a drunkard, or an extortioner; with such an one no not to eat.
2Thessalonians 3:6 Now we command you, brethren, in the name of our Lord Jesus Christ, that ye withdraw yourselves from every brother that walketh disorderly, and not after the tradition which he received of us.
This is only a part of the teaching that the Bible has on the subject. However, a pattern begins to form even with these few verses. Those who will not make things right within the church body, those who cause divisions within the church, those who live immorally, and those who walk disorderly, are to be separated from fellowship with the church. They are to be disciplined and shunned. If they do not repent, they are to be excluded from the church.
However, these negative verses clearly teach an important positive truth about church membership. Church membership should be made up of believers who have a good testimony and walk in the Christian life. They do not need to be perfect, but they must have a good testimony to the extent that they are not practicing major immorality or causing divisions in the church. There is a baseline of godliness and faithfulness that they must maintain if they are to be members.
You may wonder what this has to do with baptism, but it has much to do with it. Baptism is what people normally do immediately or soon after salvation. The Ethiopian eunuch wondered what hindered him from being baptized (Acts 8:36). Philip told him that he must first believe (Acts 8:37). After the Philippian jailer got saved, he "was baptized, he and all his, straightway" (Acts 16:33). This is a pattern seen throughout the book of Acts. Someone believes in the Lord Jesus and then they get baptized. This is why baptism has been called the first act of obedience for the believer. In this day of so much doctrinal confusion, it is understandable that some truly saved people have never been baptized. However, I have seen these people ready and willing to follow the Lord in baptism when they are told that this is God's will for them. Usually, their problem was simple ignorance of the importance of baptism.
But what of those who know that baptism is God's will for them? What if someone sits with them and shows them the scriptural teaching that baptism is the first step of obedience for the believer, that baptism is a way for them to begin following the Lord Jesus in life and practice, that it is an outward confession of their faith in the Lord and their identity with Him, and that it is a beautiful picture of the death, burial, and resurrection of Christ? What if someone sees this and then boldly refuses to be baptized? Is this person a proper candidate for membership in the local church? I think not. They are not willing to walk with the Lord in the first and most basic steps. They have not met the minimal standards of the Christian walk. Why then should they be admitted into a New Testament church?
When I take this line of reasoning and compare it with the connection made between baptism and being added to the congregation in Acts 2:41, I conclude that baptism should be a requirement for church membership. Many before me have come to the same conclusion. Those who agree are in good company. I pray this helps you see the importance of making this requirement in our churches.