Jesus foretells Peter's denial. See on Matthew 26:31, where the other references are given.
Related Commentaries of Mark 14:27
Mark 14:27-31
27 And Jesus saith unto them,All ye shall be offendedd because of me this night: for it is written, I will smite the shepherd, and the sheep shall be scattered.
28 But after that I am risen, I will go before you into Galilee.
29 But Peter said unto him, Although all shall be offended, yet will not I.
30 And Jesus saith unto him,Verily I say unto thee, That this day, even in this night, before the cock crow twice, thou shalt deny me thrice.
31 But he spake the more vehemently, If I should die with thee, I will not deny thee in any wise. Likewise also said they all.