The answer
Although St. Peter had recognized our Lord as the Son of God, until he received the Holy Spirit on the Day of Pentecost, he had not fully grasped the whole concept of Salvation and the death of our Lord on the cross. When our Lord was arrested, the disciples were afraid. "Then they all forsook Him and fled" (Mark 14:50). But St. Peter wanted to be loyal and follow his master. At the same time he realized that they were not to fight back. Therefore, not being prepared to give himself up in the way His Master had, St. Peter felt threatened and his natural instinct was to save himself from incrimination. However, as soon as he realized that he had denied Christ, he repented and cried bitterly.Answered by His Eminence Metropolitan Youssef (opens in a new tab)