In his sermon on the day of Pentecost, Peter declared: “Whosoever shall call on the name of the Lord shall be saved” (Acts 2:21). In view of this statement, folks sometimes ask: Why do members of the church of Christ insist that baptism is a requirement for being saved?
One should not assume that calling upon the Lord’s name, and being baptized, are mutually exclusive obligations. The two expressions complement one another.
Consider the following:

Calling “Lord, Lord” Not Enough

It is evident that merely “calling” on the name of Christ is not sufficient to effect salvation since Jesus Himself declared:
“Not every one that says unto me, Lord, Lord shall enter into the kingdom of heaven; but he who does the will of my Father who is in heaven” (Matthew 7:21).
Clearly, therefore, “calling” on Christ involves more than a mere verbal plea.

Calling on the Name of the Lord Includes Repentance and Baptism

In Acts 2, the same apostle who promised salvation to all who “call on the name of the Lord,” also commanded: “Repent ye, and be immersed each of you, in the name of Jesus Christ to obtain the forgiveness of your sins” (2:38).
Since the “shall be saved” of 2:21 is equivalent to the “forgiveness of sins” in 2:38, it necessarily follows that “calling on the name of the Lord” includes both repentance and baptism.

“Calling on his name” Defined

Later testimony from the New Testament makes it apparent that the person who submits to baptism, in order to receive pardon, is calling on the name of the Lord.
Note Acts 22:16. Ananias instructed the penitent Saul as follows: “And now why do you tarry? Arise, and be baptized, and wash away your sins, calling on his name.”
All who wish to enjoy the remission of past sins will call on the name of the Lord by obeying the gospel plan of redemption. In no other way is one promised pardon.
Underline “calling on the name of the Lord” in Acts 2:21 and in the margin note: Not mere words; see Matthew 7:21. Also note the harmony between 2:21 and 2:38 and write the following graphic somewhere.
calling on name — saved

repent and be baptized — remission of sins