Matthew 26:33 - Ellicott's Commentary On The Whole Bible

Though all men shall be offended. — St. Matthew and St. Mark place the boast of Peter, and the prediction of his denial, after the disciples had left the guest-chamber; St. Luke (Luke 22:23) and St. John (John 13:37) agree in placing it before. It is barely possible that both may have been repeated, but the more probable hypothesis is, that we have here an example of the natural dislocation of the exact order of events that followed one upon another in rapid sequence, and at a time when men’s minds were heavy with confused sorrow.