Message is again literally “witness” (see 1.7).

Confirms by this is more literally rendered in Revised Standard Version “sets his seal to this.” This same verb is used of God in 6.27, where Good News Translation translates it has put his mark of approval on. The metaphor used is that of placing a seal on a legal document, thus indicating approval. In New English Bible this entire phrase is translated “to attest that God speaks the truth.” Jerusalem Bible has “attesting the truthfulness of God.” New American Bible translates “certifies that God is truthful.” Goodspeed has “acknowledged that God is true,” and Phillips, “acknowledging the fact that God is true.” Moffatt translates “certifies to the truth of God.”

In the present passage it is difficult to determine precisely what is meant by the statement God is truthful. In the context of the Old Testament, such a statement would normally mean that “God is faithful (to what he has said he would do).” On the other hand, in this context the meaning may be “that what God has said is true” (see, for example, New English Bible), and so one may translate “Whoever accepts his massage has shown by this that he has accepted the message of God as true.” This meaning may also be expressed as follows: “If anyone trusts his message, he shows that he has believed that what God has said is true.”

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 .