Adam Clarke on John 5:31

If I bear witness - If I had no proof to bring of my being the Messiah, and equal to God, common sense would direct you to reject my testimony; but the mighty power of God, by which I work my miracles, sufficiently attests that my pretensions are well founded.

Bishop Pearce gives a different turn to this verse, by translating it interrogatively, thus: "If I only bear witness of myself, is not my witness true? i.e. is it, on that account, not true? In Joh 8:14, he says, Though I bear record of myself, yet my record is true. And in Joh 8:18, he says, I am one that bear witness of myself."