They kept this word in their minds, discussing with one another what it means to rise from the dead.
The disciples obediently keep this word in their mind and still do not fully grasp what Christ said. According to Jewish ideas, they could think of the general resurrection at the end of the world, but not of their Lord dying by the way of the cross and then rising again. This shows how limited their understanding was, even though they were under Christ’s direct teaching. Yet this is also comforting for us, because spiritual truths are often revealed to a person gradually. A person hears the Lord’s word, keeps it in his heart, reflects on it, and only in its proper time comes to a fuller understanding. The fact of their discussions testifies not to unbelief, but to being confused before the weight of the mystery.