And now is literally “and.” Good News Translation introduces now to indicate a transition. It is not to be taken as a temporal marker.

The words believe and know are both in the perfect tense in the Greek text (New American Bible “we have come to believe; we are convinced”). John often uses two verbs in the perfect tense, and if this tense carries any particular force in the present context, it is to indicate that the disciples were continuing in their belief and in their knowledge that Jesus is The Holy One who has come from God. However, most translations attempt to bring this out by using the present tense.

The Holy One who has come from God is evidently intended as a messianic title; in Mark 1.24 and Luke 4.34 it is the confession made by a demon who has supernatural knowledge. The nearest parallel elsewhere in John’s Gospel is in 10.36, where Jesus says that the Father chose him and sent him into the world. The verb translated chose in Good News Translation at 10.36 is from the same root as the word Holy of this verse. Most modern translators prefer to render this phrase “the Holy One of God” (New American Bible “God’s holy one”). Die Bibel im heutigen Deutsch avoids the difficulties related to the word “holy” and achieves the same effect by rendering “you are the sent one of God.”

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .