“Because he hath appointed a day, in the which he will judge the world in righteousness by that man whom he hath ordained; whereof he hath given assurance unto all men, in that he hath raised him from the dead.”
King James Version (KJV)
17:31 He hath appointed a day in which he will judge the world - How fitly does he speak this, in their supreme court of justice? By the man - So he speaks, suiting himself to the capacity of his hearers. Whereof he hath given assurance to all men, in that he hath raised him from the dead - God raising Jesus demonstrated hereby, that he was to be the glorious Judge of all. We are by no means to imagine that this was all which the apostle intended to have said, but the indolence of some of his hearers and the petulancy of others cut him short.
Ac 17:31 Because he hath appointed a day. This call to repentance is urged because God "hath appointed a day", the day of coming judgment, when the world will be judged through Christ. Of this the resurrection of Christ is an assurance. Raised him from the dead. If Jesus was raised, all men will be raised; hence, the assurance of a general judgment after death.