We need to look to the Monothelite Controversy which had to deal with whether there was one or two wills/minds in the person of Christ. The outcome was that there were two; one human and one divine with the human subjected to the divine. The eternal Son of God did not assume a part of a human nature without a mind, without a will, without human activity, but He assumed all the things that were planted in our nature by God.
Now then, to act (or in this case, speak) is the work of a person, but the form or nature is the cause of this action; for each person acts in accord with the form or nature which it has. A difference in causes (natures) produces a difference in effects (actions). Therefore, where there are different natures, there are also different activities. So in the one Person of Christ there are two natural actions, the divine and the human, each of which has its own essential attributes, functions, and actions. Jesus was thirty years old (according to His human nature Luke 3:23); according to His divine nature He could say: "Before Abraham was born, I am" (John 8:58). The question is did both natures know this and communicate it to the Person. The answer is yes because the divine nature with its corresponding divine will willed the human nature to respond in such a fashion in keeping with Christ's office and ministry. In the text regarding Mark 13:32, we have a slightly different situation here. Christ is acting (speaking) from His human nature, but, this time, the divine will does not allow the human will access to this knowledge. For this information is not to be published on earth. Therefore, as man, Christ cannot answer the question.
