Commentaries:
Robertson's Word Pictures (NT)
Out of the law (ek tou nomou). That is, "out of the Scriptures" (John 10:34; John 15:25).
The Christ abideth forever (o Xristov menei eiv ton aiwna). Timeless present active indicative of menw, to abide, remain. Perhaps from Psalms 89:4; Psalms 110:4; Isaiah 9:7; Ezekiel 37:25; Daniel 7:14.
How sayest thou? (pwv legeiv su). In opposition to the law (Scripture).
The Son of man (ton uion tou anqrwpou). Accusative case of general reference with the infinitive uywqhnai (first aorist passive of uyow and taken in the sense of death by the cross as Jesus used it in verse John 12:32). Clearly the crowd understand Jesus to be "the Son of man" and take the phrase to be equivalent to "the Christ." This is the obvious way to understand the two terms in their reply, and not, as Bernard suggests, that they saw no connexion between "the Christ" (the Messiah) and "the Son of man." The use of "this" (outov) in the question that follows is in contrast to verse John 12:32. The Messiah (the Son of man) abides forever and is not to be crucified as you say he "must" (dei) be.
Other Robertson's Word Pictures (NT) entries containing John 12:34:
John 1:29
John 3:14
John 8:28
John 10:34
John 12:2
John 15:25
John 20:9
2 Peter 3:18
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