I am going to try to get this point across without sounding like a jerk.
Circumcision was for boys and men only, while baptism is for both sexes alike. Circumcision was for every boy or man of Hebrew blood, while baptism is only for saved people. Circumcision and baptism mean entirely different things. Circumcision meant that this child was an Israelite, one of the chosen race by natural birth. Baptism means that the one baptized is born again and one of God's children by a birth from Heaven. One has no right to be baptized until he is born as God's child. The Bible does not say one word about dedicating little children to the Lord by any kind of Christian ceremony and certainly does not mention baptism of babies anywhere in the Bible.
Baptism of an unaccountable baby does untold harm. For one thing, it leaves the impression that the change of heart is not necessary. It leaves the impression that the religion of the Lord Jesus is a matter of ritual, not of personal faith. It ignores the Bible teaching that baptism represents the burial and resurrection of Jesus and the believer's change of heart. Worst of all, the one who is thus given a ceremony which was only for Christians, often is led to believe, in after years, that since he is a member of a church, has been baptized, and is a respectable citizen, therefore he does not need the change of heart, does not need to be converted, saved by the blood of Jesus. Whatever fine argument you may make for the sprinkling of a little baby, it is answered by the plain, indisputable fact that Jesus did not command it and it is certainly unscriptural and wrong.
Also, this is a little random fact, but just another way for non believers to know the awesome power of God and how medical science PROVES his existence. It states in Genesis that the newborn males should be circumsized on the 8th day.
I used to wonder why the 8th day was so important then I read that Vitamin K(which is pretty much what clots blood) doesnt become present in a baby until after they are 5 days old.....usually 5 to 7 days...which by the 8th day the Vita K is certainly present... Neato huh?