Joel 2:28 - Ellicott's Commentary On The Whole Bible

I will pour out my spirit upon all flesh. — Holy Scripture is itself the interpreter of this most weighty promise. St. Peter’s quotation and application of it in the Acts is its commentary. “Afterward “ — LXX., after these things becomes in the apostle’s mouth — “in the last days” — i.e., in the Christian dispensation, when, after the punishment of the Jews by the heathen, their king came — “my Spirit” — St. Peter renders “of my spirit,” after the LXX., indicating the gifts and influences of the Holy Ghost — “upon all flesh” — i.e., without distinction of race or person — “they of the circumcision were astonished because that on the Gentiles also was poured out the gift of the Holy Ghost.” The outward manifestation of these gifts, as shown on the Day of Pentecost, in accordance with this prediction, was gradually withdrawn from the Church; the reality remains.