FV proponents consistently assert that the act of water baptism is an efficacious means of uniting the recipient to Christ. You can follow a debate here--notice the way in which baptism is referred. This doesn't square at all with the Reformed confessions because the FV wants a wholesale redefinition of the nature of a sacramental sign. HC Q&A 65 asks, “Since then we are made partakers of Christ and all his benefits by faith only, whence does this faith proceed? Answer: From the Holy Ghost, who works faith in our hearts by the preaching of the gospel, and confirms it by the use of the sacraments.
Notice carefully how the Q&A speaks of the sacrament, it only confirms, it does not create or confer. What the FV wants to do with baptism requires the complete redefining of the nature of a sacrament, not as a sign and seal to confirm, but as an instrument to confer. Baptism is a means to signify grace and confirm grace, it is not the instrument of bestowing grace; this is contrary to the nature of a sign. The efficacy of the sacrament is the efficacy of the sign and the seal, and only this. This is why Calvin said the seals which are attached are nothing taken by themselves, yet when added to the writing, they seal what is written ( Ins. 4:14:5).
The reader should not be mistaken by FV language; for all their waxing eloquent on these disctinctions, they leave us in mass confusion. The Reformed have always been clear about the proper way of speaking about sacramental efficacy. Notice the crucial distinctions VanMastricht makes as he explains baptismal efficacy:
1. The efficacy of baptism consists in its sealing, agreeably to the nature of all sacraments so far as they are seals (Romans 4:11, which presupposes regeneration as the principle of faith).
2. The pollution of the soul is not purged away by the baptism of water ( I Peter 3:21), therefore regeneration is not confined thereto.
3. If this was the case, all the baptized would be regenerate, and that at the very time of their baptism. The Scriptures speak against this (Acts 8:13, 20-21, 23), and also experience shows that many baptized persons live most abandoned lives, and are not finally saved. We read also of persons regenerated before their baptism, such as the eunuch (Acts 8:36-37), the centurion and his family (Acts 10:2, 22), yea, of those who were never baptized at all, such as the thief on the cross (Luke 23:42-43). According to the common observation, it is not the want of baptism, but the contempt of it that is damning.
4. Regeneration is limited to no sacrament, not to circumcision (Romans 2:25, 27-28), nor to the Passover (1 Corinthians 10:3-4), nor to the Lord's Supper (I Corinthians 11:27), nor to any legal washings (Hebrews 9:10; 10:4), and therefore not to baptism, since it is expressely said that even a baptized person, if he beleives not, shall be damned (Mark 16:16). I will only add that
5. The Holy Ghost is said to regenerate according to his sovereign pleasure: "As the wind bloweth where it listeth..so is everyone born of the Spirit (John 3:8).
...Our opponents [Roman Catholics] on the other side argue from the text; "know ye not that so many of us as were baptized into Jesus Christ were baptized into his death?" (Romans 6:3). To this I answer, this text means only that all the elect, being true believers, baptized according to the institution, have communion and participation in the death of Christ, which is sealed to them by baptism. But it is not said that this communion is effected particularly by baptism, much less that this communion is absolutely connected by baptism.