Luke 24:44  And He said to them, These are My words which I spoke to you while I was still with you, that all the things written in the Law of Moses and the Prophets and Psalms concerning Me must be fulfilled.  (45)  Then He opened their mind to understand the Scriptures;  (46)  And He said to them, Thus it is written, that the Christ would suffer and rise up from the dead on the third day. 

Just as the Man-Savior had opened the Scriptures to the disciples on the way to Emmaus, He now opened the Word to those gathered in the room. He also opened their minds to understand the Scriptures… (vv. 44-45). The Law of Moses, the Prophets, and Psalms are the three sections of the entire Old
Testament, that is, all the Scriptures (v. 27). The Savior’s word here unveils that the entire Old Testament was a revelation of Him and that He was its center and content. The fact that He opened the mind of the disciples indicates that in order to understand the Scriptures our mind needs to be opened by the Lord Spirit through His enlightening (Eph.1:18).

In verse 46 the Man-Savior went on to say to the disciples, “Thus it is written, that the Christ should suffer and rise up from the dead on the third day.” Here the Lord seems to be saying, “When we were in Galilee, I told you that I would die and then be raised up on the third day. But you did not understand what I was talking about. Now I am opening up the Word to you, and I am also opening your eyes.”

I believe that it was from the time of this appearing of the Lord that Peter began to be transformed. At least he began to understand the Word. Therefore, in chapter one of Acts Peter could stand up among the one hundred and twenty and interpret the Scriptures in the right way. In Acts 1 we do not see a natural Peter as we do in Luke 22. Instead, we see another Peter, a regenerated and transformed Peter. That was the situation of all the disciples in Acts l.