Peter had begun the first anointed message of the Early Church. After assuring the assembly of clueless Jews outside that the 120 were high on the Holy Spirit, not wine, he declared prophetic fulfillment!
Ch 2: LESSON 15
16 “But this is what was spoken of through the prophet Joel: 17 ‘AND IT SHALL BE IN THE LAST DAYS,’ God says, ‘THAT I WILL POUR FORTH OF MY SPIRIT ON ALL MANKIND; AND YOUR SONS AND YOUR DAUGHTERS SHALL PROPHESY, AND YOUR YOUNG MEN SHALL SEE VISIONS, AND YOUR OLD MEN SHALL DREAM DREAMS; 18 EVEN ON MY BONDSLAVES, BOTH MEN AND WOMEN, I WILL IN THOSE DAYS POUR FORTH OF MY SPIRIT And they shall prophesy.” 
This was not to be a one time occasion for a few but an all time occasion for everyone. The Upper Room experience would be universal from that time forward throughout the Church Age until the present, dependent only on following the prototypical example of the originals as they followed to the letter the teachings of the Lord Jesus.
THE PROPHET JOEL
There is no consensus regarding the time Joel lived. Various dates have been given. It was most likely before the Babylonian exile. A good case can be made for the early 600s BC. Whatever the case, the Lord anointed Peter to use the writings of this relatively obscure Hebrew prophet as the first Scriptural reference in the very first message ever delivered. One might notice that he chose the prophetic and not the priestly. Until John the Immerser there had been no prophet in Israel since the death of Malachi over four centuries earlier. In that non-prophet gap the priests had finally achieved their dream and had taken over. They substituted their own word and natural reasoning over the anointed message of the prophet. It caused a downward slide they never recovered from, even to the point of killing the greatest Prophet of all.
Joel said something far out would happen in the Last Days, meaning the final days of what was left of the Israelite nation. He spoke of not just a few prophets but many, and they would also include women. Is this not awesome? He also spoke of great celestial signs in the sky, fully observable, epochal, and dripping with spiritual portent:
19 ‘AND I WILL GRANT WONDERS IN THE SKY ABOVE AND SIGNS ON THE EARTH BELOW, BLOOD, AND FIRE, AND VAPOR OF SMOKE. 20 ‘THE SUN WILL BE TURNED INTO DARKNESS AND THE MOON INTO BLOOD, BEFORE THE GREAT AND GLORIOUS DAY OF THE LORD SHALL COME.’
Peter finished this portion with a flourish, telling the vast assembly before him that the Lord’s hand is not too short to save! His ear is not too dull to hear! He extends the promise of Joel to everyone both then and now:
21 ‘AND IT SHALL BE THAT EVERYONE WHO CALLS ON THE NAME OF THE LORD WILL BE SAVED.’” 
© 2020 by RJ Dawson. All Rights Reserved.
 Please note that the use of all caps in the NASB denotes Old Testament passages occurring in the New Testament.
 Unless otherwise noted all Scriptures are taken from the New American Standard Bible, © 1960, 1963, 1968, 1971, 1972, 1973, 1975, 1977, 1995 by The Lockman Foundation. Used by permission.