The small group study guide for Robert Morris’ “The God I Never Knew” contains the following assertion:

Before that day [Pentecost], they struggled to understand the Scriptures. Afterward, they realized that the entire Old Testament pointed prophetically and symbolically to the life and redeeming work of Jesus. What had previously been shrouded in mystery suddenly became clear. (Morris, p. 82)

However, Luke 24:44–49 tells us something different:

He said to them, “This is what I told you while I was still with you: Everything must be fulfilled that is written about me in the Law of Moses, the Prophets and the Psalms.”

Then he opened their minds so they could understand the Scriptures. He told them, “This is what is written: The Messiah will suffer and rise from the dead on the third day, and repentance for the forgiveness of sins will be preached in his name to all nations, beginning at Jerusalem. You are witnesses of these things. And behold, I am sending the promise of my Father upon you. But stay in the city until you are clothed with power from on high.”

Here, we see Jesus opening the minds of his disciples to the Scriptures before His ascension—that is—before the Day of Pentecost recorded in Acts 2. Therefore, to make his case for speaking in tongues, Morris has rearranged the chronology of Scripture.

…examining the Scriptures daily to see whether these things were so. Acts 17:11