Matthew Poole and continuators on John 12:34

34 The people answered him , We have heard out of the law, that Christ abideth for ever: and how saist thou, The Son of man must be lift up? Who is the Son of man ?

Here again the Law is taken in a larger sense than in some places, where it is onely significant of the Books of Moses, in opposition to the Prophets and other holy Writings, as we had it before, Chap. 20.34. for the places of Scripture which the people seem to refer to, seem to be Psal. 110.4. where Christ is called a Priest for ever; or else to Dan. 7.14. where the Kingdom of the Messiah is said to be an everlasting Dominion, which should not pass away, a Kingdom that should not be destroyed: so also, Dan. 2.44. Micah 4.7. These old Prophecies of the Messiah, the people could not reconcile to what our Saviour here told them of his Death; the reason was, their understanding the true Notion of the Messiah, and of his Kingdom, which they fancied not to be a Spiritual and an Eternal Kingdom, but a Temporal Kingdom here on Earth. This made them ask, how (that is, with what consistency to those Prophecies) if he indeed were the Messias, he said, The Son of man should die, (for that they understood by the term lifted up) which maketh it very plain, that it was a phrase they used to express that kind of Death by. They ask who he meant by the Son of Man.

Marginal references: Psal. 89.36, 37. Isa. 9.7. & 53.8. Eze. 37.25. Dan. 7.14, 27.