Since ye seek a proof of Christ speaking in me - see the notes on the previous chapters. They had called in question his apostolic authority; they had demanded the evidence of his divine commission. He says that he would now furnish such evidence by inflicting just punishment on all offenders, and they should have abundant proof that Christ spoke by him, or that he was inspired.
Which to you-ward is not weak - Or who, that is, Christ, is not weak, etc. Christ has manifested his power abundantly toward you, that is, either by the miracles that had been performed in his name; or by the diseases and calamities which they had suffered on account of their disorders and offences (see the note on 1 Corinthians 11:30); or by the force and efficacy of his doctrine. The connection, it seems to me, requires that we should understand it of the calamities which had been inflicted by Christ on them for their sins, and which Paul says would be inflicted again if they did not repent. The idea is, that they had had ample demonstration of the power of Christ to inflict punishment, and they had reason to apprehend it again.