More than any other living soul, Mary knew this was the virgin born son of God. Even Joseph needed divine revelation to inform him of this miracle. Mary's best friends may have whispered behind her back. But Mary was specifically told by the angel, and she was the thoughtful type. She is known to keep all these things and ponder them in her heart. She told the servants to do whatever he ordered when he began his ministry of miracles in Cana by changing water into wine. She believed in him. Later we will see Mary numbered with the roll of the first church in Jerusalem along with the other disciples and apostles. She is definitely a believer.
But at the cross even believers were stunned. Peter had recently rebuked Jesus for suggesting that He--the Messiah--must die and rise again. His understanding of prophesy promised the Son of David to reign forever. Mary must have shared some of that confusion. Disciples on the road to Emaus remarked that "we had hoped that he was the one to redeem Israel."
Whatever else was on her mind, Mary must have remembered that somber prophesy of aged Simeon at the time of Jesus' birth that a sword would pierce her own soul. Through her tears, Mary surely felt the thrust of that sword, loving Jesus, her precious son, and yet knowing him to be her mighty Lord as well. She did not yet know that He had to be made sin for us so that we might be made the righteousness of God in Him. Even though we know that much more than did Mary before the cross, we are still left without anything intelligent to say when we hear our Jesus cry out, "My God, my God, why have you forsaken me?" It is a scene for us to witness, but not to comprehend with exhaustive satisfaction. There is always mystery when we hear God talking to God.
But there was a special word for Mary. "Woman behold your son." At first she felt a stab of pain as she looked at her little boy now helplessly impaled, drawing her attention with his words. But then he said to John, "Son, behold your mother." And they both understood that even in his death, Jesus was keeping the law of God by honoring his mother and consigning her to John's care.
So we now can see both the active and passive obedience of Christ in this scene. He kept the whole law for his people and suffered the punishment due to their sins. That is a good day. It is Good Friday.