One of the first works of the Resurrected Christ was not the operation of a spectacular miracle, but the opening of his disciples’ minds, to make them able to understand the Scriptures (v. 45).
The Lord had accomplished a great number of miracles in the course of his ministry; that was insufficient to make his disciples understand the necessity of the crucifixion, planned and announced in the Holy Scriptures. Would new miracles, after the resurrection, be able to enlighten them? It’s far from certain! What was necessary was a divine intervention directly on their intelligence.
So, simply, and like the Creator in the beginning (Genesis 2:7), Jesus breathes on them (John 20.22) and “opens their minds”: from that point on, all became new for them. They finally understood and agree to believe that everything that had happened up to then had been foreseen in the Scriptures.
They were transformed inside and their entire life was marked by it.
When a man’s mind is opened by the Lord to understand the Bible, all miracles are possible, and especially that of the radical transformation of the human heart. That is why, when we read: “He opened their minds,” we are in the presence of what was perhaps the greatest miracle Jesus accomplished.