It is written in your Law may be translated “there are words in your laws which say” or “your Law contains these words.” What follows must then normally be given as direct discourse.

The pronoun your (New English Bible “your own”) is emphatic. Jesus is pictured as at once hostile to their law and superior to it.

In the Jewish context the two witnesses would normally be taken to be two witnesses other than the person actually concerned. However, in the following verse Jesus makes himself one of the witnesses on his own behalf. The Scripture passages referred to are Deuteronomy 17.6 and 19.15.

When two witnesses agree, what they say is true is literally “the testimony of two men is true”; Die Bibel im heutigen Deutsch renders “If two witnesses agree in their testimony, the truth results.” Good News Translation restructuring transforms the noun-orientated structure “the testimony of two witnesses” to a verb phrase when two witnesses agree, which then requires the inclusion what they say.

The clause when two witnesses agree may be rendered as a condition, “if two witnesses agree” or “if two witnesses say the same thing” or “if the words of two witnesses match one another.”

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 .