Question

Is there biblical evidence to support the statement that baptism is required before partaking in communion?

Answer

Good question. I think you might begin here: under the Old Covenant, you had to be circumcised in order to be able to partake of the Passover meal. Exodus 12:48 says "If a stranger shall sojourn with you and would keep the Passover to the LORD, let all his males be circumcised. Then he may come near and keep it; he shall be as a native of the land. But no uncircumcised person shall eat of it."

The New Testament describes Christ as our Passover Lamb (1 Cor 5:7). The Lord's Supper is both a memorial of his sacrifice as our Passover Lamb, and a means of grace by which we partake of Christ's body and blood (1 Cor. 10:16). Now, since Baptism replaces circumcision as a sign of the covenant, the sign of our being admitted into that covenant and united to Christ (Col. 2:9-12), though it is not necessary to salvation (the thief on the cross was not baptized) it is a sign we are commanded to receive. Disobedience to Christ in this area is a sin and Paul warns us in 1 Corinthians 11 that we are not to come in an unworthy condition to the Lord's table (1 Cor 11:27). Therefore Baptism would then be seen as a requirement for all who would partake of communion.

More simply, why would you not want to be baptized? Is it shame for being identified or joined to Christ, a desire to not confess him? If that is so, why would you want to come to the Lord's Supper?

I hope this helps you in your thinking.