"And it shall come to pass in the last days, says God, that I will pour out of My Spirit on all flesh, your sons and your daughters shall prophesy, your young men shall see visions, your old men shall dream dreams. And on My menservants and on My maidservants I will pour out My Spirit in those days; and they shall prophesy. I will show wonders in heaven above and signs in the earth beneath: blood and fire and vapor of smoke. The sun shall be turned into darkness, and the moon into blood, before the coming of the great and awesome day of the LORD. And it shall come to pass that whoever calls on the name of the LORD shall be saved'" (Acts 2:17-21).
Upon whom would the Holy Spirit be poured out in the last days? The answer: "All flesh" (Acts 2:17). One might initially think that "all flesh" means every human being would be a recipient of the Spirit, but such is not correct. In 2:18, God declared that His Spirit would be poured out "on My menservants and on My maidservants." That certainly is not"all flesh" since such would exclude rebellious sinners (i.e., those who weren't His servants). We can learn elsewhere that not even all Christians received a miraculous measure of the Spirit (cf. I Cor. 12:29,30). So, the evidence is clear that certainly not every single person would receive an outpouring of the Spirit. Well Stephen, if "all flesh" doesn't mean everybody, what does it mean? Simply this: God's Spirit would be poured out on all types of flesh. Some of the details of Joel's prophecy hint at this (e.g., sons and daughters would prophesy and the young would see visions while the old would dream dreams). As the book of Acts unfolds, we will see all categories of people being blessed with miraculous abilities from the Spirit (Jew and Gentile, men and women, and young and old; cf. Gal. 3:28). Initially, the Spirit was poured out upon the apostles and soon the Spirit's gifts would be shared with others also in a special way.
Joel's prophecy also speaks of a time when God would show "wonders in heaven above and signs in the earth beneath" (Acts 2:19). He mentions blood, fire, smoke vapor, the sun being darkened, and the moon being turned to blood. I believe this is apocalyptic language and should not be understood literally. Such language was employed in Hebrew literature to depict the downfall of powers upon whom the Lord was to visit in judgment (e.g., Isa. 34:4,5; 13:10; Eze. 32:7,8). When a nation was to be punished by God, vivid descriptions like these (of a cosmological nature) were often used. There was a "good side" to Joel's prophecy (great blessings through the Spirit), but there was also a "bad side" (of impending judgment and destruction).
What great downfall and time of divine judgment is being predicted here? There are two main positions favored by conservative Bible scholars. Some believe Jerusalem's destruction in AD 70 is in view. In the destruction of Jerusalem, God executed His wrath on the rebellious nation of Israel. Such a view is consistent with other Old Testament uses of the phrase "the day of the LORD," meaning a day of great calamity for the opponents of God (cf. the beginning of Matt. 24). Others, however, believe the second coming of Christ is in view. This, too, will be a great and awesome day of the Lord (cf. II Pet. 3:10-13). All the dead will be raised and judged by the Lord. There will be great rewards and punishments administered. This view is consistent with other New Testament uses of "the day of the Lord," all of which point to the end of the world. I prefer the second view since its scope and applicability are broader than just the inhabitants of Jerusalem. The pouring out of the Spirit would ultimately affect all types of people throughout the world, and such is also the case for "the great and awesome day of the LORD" under consideration, in my opinion.
The quote from Joel ends with this statement - "Whoever calls on the name of the LORD shall be saved." I believe the reference here is to salvation from sin, but how does one call on the name of the Lord? There is much confusion about this matter in our modern age, and we will investigate it in-depth after considering Acts 2:38.