On p. 55 of the Jehovah's Witnesses publication, Reasoning from the Scriptures, we read the following under the heading of "Does Christian water baptism result in the forgiveness of sins?"
1 John 1:7: "If we are walking in the light as he himself is in the light . . . the blood of Jesus his Son cleanses us from all sin." (Thus, not baptismal water but the blood of Jesus cleanses us from sin.)
There are a number of problems with using this passage against baptismal regeneration.
Firstly, John 3:1-7, written by the same author, teaches baptismal regeneration, notwithstanding the common eisegesis of opponents of this doctrine.
Secondly, no one denies that the meritorious cause of salvation is the sacrificial death of Jesus. The author(s) of this piece ignores the distinction between instrumental means of (initial) justification and the meritorious cause thereof, a common error one finds amongst those who deny baptismal regeneration (not just Jehovah’s Witnesses). Indeed, in water baptism, it is not the water per se, but the God working through the water and applying the merits of the atonement to the individual that brings about the remission of one’s sins. Such is explicated in passages such as Acts 2:38.
Thirdly, absolutising this passage in the way critics do, they will have to argue that faith alone does not save, let alone confession of Christ (“calling upon the name of the Lord”), etc. Instead, it is “the blood of Christ.” One is obviously question-begging when they claim it is the blood/sacrifice of Christ that merits salvation—all parties agree, however, one is begging the question vis-à-vis the application thereof.
Furthermore, absolutising the passage, one will have to argue that God does not bring about salvation, but it is the blood of Jesus alone. As one commentator noted:
Here in verse 7, however, it is not God but blood that purifies. Within the sacrificial system the manipulation of blood played a central role (e.g., Lev 16:15-19). Whatever the origins of this, there is rarely any attempt in the biblical texts themselves to interpreter how or why the blood “works”; instead it is seen as part of the mechanisms that God has provided for the proper response to God, and especially for the restoration of right relations with God. It is within this framework that Lev 17:11 says that blood if the life of all flesh and that God has given it on the altar as a means of forgiveness (or atonement). So understood, it is not the blood that has been shed itself nor the death of the animal that it represents, that effects forgiveness, but God through the divine grace, and this means that there can be no automatic equation between the sacrificial shedding of blood and the granting of forgiveness. (Judith M. Lieu, I, II, and III John: A Commentary [New Testament Library; Louisville, Ky.: Westminster/John Knox Press, 2008], 56)
While much more could be said, it is clear that, as an argument against baptismal regeneration, the use of 1 John 1:7 rests on eisegesis and question-begging premises, as well as ignoring texts that explicitly teach baptismal regeneration, including from the writings of the same author of the epistle!