Note 2 at Ac 2:16: Peter here exhibited a perception and understanding of the Scriptures that had not been characteristic of him or the other disciples before. This came as a direct result of the baptism of the Holy Spirit. Jesus said that the Holy Spirit would lead us into all truth and teach us all things (Joh 14:26 and 16:13), and this is exactly what was happening with Peter.

Receiving the baptism of the Holy Ghost is the single most important key to receiving revelation knowledge from God (see note 1 at Lu 2:26 and note 1 at Joh 7:15).