Re-read Romans 4:1-8.
Paul, filled with the Spirit, introduces the example of Abram/Abraham, introducing him with the Jewish title "our forefather". We hear that Abraham was made righteous because of his belief. Abraham was justified by faith, not by his works. This leads to the next section of the chapter.
Read Romans 4:9-12.
Paul now preempts a question that the first 8 verses lead to. That question is "wasn't Abraham justified because he was circumcised?"
To answer this Paul takes us through the timeline of the story of Abraham and God in relation to the righteousness credited to Abraham and the covenant of circumcision. The idea of being credited, that is forgiven for our transgressions and having our sin covered, not by our works but by God's grace, through faith.
[God] took him outside and said, “Look up at the sky and count the stars—if indeed you can count them.” Then he said to [Abram], “So shall your offspring be.” Abram believed the Lord, and he credited it to him as righteousness. (Genesis 15:5-6)
What we see is that God credited Abraham as righteous because he believed. What we read in Genesis 17 (2 chapters on, but also approximately 14 years on from chapter 15 is the introduction of the covenant of circumcision.
When Abram was ninety-nine years old, the Lord appeared to him and said, “I am God Almighty; walk before me faithfully and be blameless. Then I will make my covenant between me and you and will greatly increase your numbers.” Abram fell facedown, and God said to him, “As for me, this is my covenant with you: You will be the father of many nations. No longer will you be called Abram; your name will be Abraham, for I have made you a father of many nations. (Genesis 17:1-5)
This is my covenant with you and your descendants after you, the covenant you are to keep: Every male among you shall be circumcised. (Genesis 17:10)
Therefore we can see that God recognised Abraham as righteous before - 14 years before - introducing the covenant of circumcision. Paul, therefore, answers this Jewish misconception that the act of circumcision (i.e. works) plays a part in justification, that is salvation. It doesn't!
Now, that we have unpacked the timeline presented in the Word of God, we are often faced with our own misconception, is baptism the replacement for circumcision?
Have we replaced an Old Testament ritual with a New Testament ordinance?
Have we replaced a physical act with a symbolic ceremony?
After all, circumcision (for men) was a sign that they belonged to God's old covenant people, while baptism seem to be the equivalent new covenant sign.
The answer is that in the Word of God, in particular the New Testament, we actually see circumcision as a metaphor for conversion, while baptism is a result of conversion. It is true that baptism, along with the Lord's supper (communion) are the two ordinances that Jesus gave to His church. But when a believer first accepts Christ and follows and walks with Jesus, they are saved at that point, and baptism isn't the moment of salvation. What baptism is, is the result of that faith. A believer would be driven to baptism as a demonstration of their faith. A person is baptised, not to be saved, but because they are saved!
We believe that in scripture we are clearly taught that water baptism, by immersion, is an act of obedience to the command of Jesus. Those who have confessed their faith in Christ are baptised in the name of the Father, the Son and the Holy Spirit. We believe that by faithfully following this command we proclaim our new standing as a child of God, As the Saviour was buried and raised again so is the believer buried with Him in a death like His and raised again into newness of life. We believe that the scriptures do not teach that baptism is a cleansing of sin but is one of two sacraments instituted by our Lord.
Also read: Matthew 28:19, Romans 6:3-6, Colossians 2:12, Acts 2:41, Mark 16:15-16.