1 John 5:8 And there are three that bear witness in earth, the Spirit, and the water, and the blood: and these three agree in one.
As we saw in the previous verse , here it is making reference to the confirmation that three also bear witness in the earth. The Spirit, which is the Holy Spirit, that Jesus told he would send to comfort us. Again the water because we symbolize our accepting Christ as our savior with a baptism in water because of the example He set for us. Also the blood because the blood Jesus shed for us on that cross covers all our sin. Just as in verse 7 we see that all three are together as on in spirit all together they agree as one about the statement in this verse. All three are necessary to be a Christian..