I have never read commentaries on 1 John 5:6-8 but as I said, I have been reading it again and I came to the above passage.
The wording is peculiar, and I tried to impose the means of grace in this reading: Here is how I take it...The Spirit of Truth is the Word, water - stands for Baptism, and blood for the Lord's Supper. It seems it makes sense to me. Now so I picked up a reading from a commentator, who referred this to the Atonement of Jesus.
Whereas it is noble idea, I prefer the means of grace reading of this and I find I am not alone. Harold Lindsell's comments referred to this as the ordinances so named.
But being what I am - I connect this to the means of grace - Word, Baptism, Supper.
I believe this concept of means of grace have been around when the Epistles were being written that is why you cannot do raw exegesis, at the end, your hermeneutic has to kick in on the means of grace. Why? Because the disciples had this notion earlier in our history already. Read the NT with that hypothesis and it does not do damage to anything in its internal consistency.
Take a look.