Acts 2:19-21 meaning

Peter continues to quote the prophet Joel, listing God's promised signs that will happen in the "last days" when He has poured forth of His Spirit onto all mankind (Acts 2:17-18). The following signs are to occur in the very last days that take place Before the great and glorious day of the Lord.

Peter says the prophecy of Joel is what is "spoken of" (Acts 2:16). Peter does not say the prophecy is fulfilled; the complete fulfillment of Joel's prophecy is yet to come. Peter does reference Joel's prophecy as an explanation for what is happening in Jerusalem. God has begun to pour out His Spirit. The pouring out started then, and has continued for new believers even to this day. In our current era, the Holy Spirit indwells every new believer at their point of belief (Ephesians 1:13-14). However, in the Acts era the Holy Spirit indwelt Gentiles upon initial belief, but fell on Jews upon their repentance, sometimes as evidenced by baptism. The Holy Spirit falling on the Jewish disciples waiting in the upper room might be an exception to this rule, although they were waiting in obedience, which showed a repentant heart.

During this age when God's Spirit lives among men, there are other signs that will follow, and all of these signs will come before the day of the Lord. The term day of the Lord refers to any season of judgement from God. The Babylonian exile was God's judgement on Israel, and is spoken of as a "day of the Lord." This Joel prophecy likely speaks of the day of the Lord that is the final Judgement Day. This day is spoken of throughout the Scriptures. The book of Hebrews exhorts believers to gather together to stir one another up to love and good works, and "all the more as you see the day drawing near." In the context this seems clearly to speak of the final day of judgement. This concept is clearly taught in the Old Testament as well, as illustrated by this passage from Ecclesiastes:

"For God will bring every act to judgment, everything which is hidden, whether it is good or evil" (Ecclesiastes 12:4).

In his first letter to the Thessalonians the Apostle Paul refers to the day of the Lord in context of discussing the second coming of Jesus (2 Thessalonians 4:13 - 5:2). This makes sense, given that it will be Jesus who will judge the earth (Acts 17:30-31).

From Joel's prophecy we see that preceding this day there will be many elemental wonders, both in the sky above and on the earth below. There will be Blood, and fire, and smoke, all signs of warfare and destruction. Such devastation describes an earth in turmoil; things are at their very worst just before God's day of judgement. Revelation predicts this ultimate crisis that will come upon the earth (Revelation 14:20, 18:18, 9:18), prior to a culmination where the existing heavens and earth will be consumed in fire (2 Peter 3:12).

Before this great and glorious day of the Lord, we are told that the sun will be turned into darkness
 and the moon into blood. Again, this is imagery of the world spinning into total darkness and despair. It is also possible that these signs are the result of Jesus returning with His heavenly army to judge humankind's sin and put an end to evil (Matthew 24:29-30, Revelation 19:11-21).

Whatever the Blood, fire, and smoke are the result of, they are consistent with the mood of the day of the Lord as told elsewhere in scripture. Amos the prophet describes the day of the Lord grimly, "Will not the day of the Lord be darkness instead of light, Even gloom with no brightness in it?" (Amos 5:20).

Peter later describes the day of the Lord in his second letter to the church, "But the day of the Lord will come like a thief, in which the heavens will pass away with a roar and the elements will be destroyed with intense heat, and the earth and its works will be discovered" (2 Peter 3:10).

With this serious reminder that eventually God will bring all men to account for their deeds, and will do away with the old earth, Peter is directing his listeners toward repentance for rejecting Jesus. He is trying to persuade them to return to God and ask for forgiveness. So he finishes quoting Joel with this final, encouraging point: And it shall be that everyone who calls on the name of the Lord will be saved (Joel 2:30-32a).

The people must call on the name of the Lord to be saved from His judgement. Peter will explain to the crowd in great detail why they must call on the name of the Lord, because of their rejection of Jesus the Nazarene, who was in fact the Son of God. If they are to escape the judgement that will come on the Day of the Lord, they must embrace the truth of who Jesus was, and call for forgiveness from God by repenting, thus they will be saved. The word saved should be interpreted in context, to determine what is being delivered from what. In this case, it seems best to fit that those who call on the name of the Lord will be delivered from adverse judgement during God's final judgement.