matthew 16:21 From that time forth began Jesus to shew unto his disciples, how that he must go unto Jerusalem, and suffer many things of the elders and chief priests and scribes, and be killed, and be raised again the third day. - Free Bible Online

      Announcement of His Approaching Death and Rebuke of Peter (Mt 16:21-28).

      The occasion here is evidently the same.

      21. From that time forth began Jesus to show unto his disciples--that is, with an explicitness and frequency He had never observed before.
      how that he must go unto Jerusalem and suffer many things--"and be rejected," (Mr 8:31; Lu 9:22).
      of the elders and chief priests and scribes--not as before, merely by not receiving Him, but by formal deeds.
      and be killed, and be raised again the third day--Mark (Mr 8:32) adds, that "He spake that saying openly"--"explicitly," or "without disguise."

JFB.