“reward.” The Greek is misthos (#3408 μισθός), and it refers to a payment made for work done; wages. As “wages” or “payment,” it can refer to either a reward (cp. Matt. 5:12; 10:41; Luke 6:35; 1 Cor. 3:14) or a punishment (2 Pet. 2:13), depending on what kind of “payment” is due. In the future Millennial Kingdom, when Jesus Christ rules as king on the earth, people will be repaid for what they have done in this life (see commentary on 2 Cor. 5:10, “good or worthless”). Some people might think they have done very little to support God’s work, but if anyone has helped accomplish God’s work on earth, he will be amply rewarded.
In Matthew 5:12 and some other verses, the reward is said to be “in heaven.” The Bible makes it clear that, with the exception of Christians, who are in the Rapture, believers from Old Testament times get up from the dead and live on the earth. Ezekiel 37:12 (KJV) says, “Thus saith the Lord GOD; Behold, O my people, I will open your graves, and cause you to come up out of your graves, and bring you into the land of Israel.” There is no verse in the Old Testament that states that people go to heaven to live forever. The OT states that when people are resurrected they live on earth.
The rewards that people would receive for their works were said to be “in heaven,” meaning, in God’s keeping. God is keeping a record of people’s deeds, and is thus said to be storing up either the reward, or the punishment, that the person deserves and will receive after the Day of Judgment when Jesus is reigning as king on the earth.
It is understandable that Matthew 5:12 and other verses like it, which speak of rewards, treasures, or even a home in heaven, can be confusing and may lead one to believe that righteous people go to heaven when they die. These include verses such as Matthew 5:12 (“Great is your reward in heaven”), Matthew 6:20 (“store up for yourselves treasures in heaven”), Colossians 1:5 (“The hope that is stored up for you in heaven”) and 1 Peter 1:4 (“Kept in heaven for you”). However, Jesus was talking to Jews who knew (or should have known from the Old Testament scriptures) that they would inherit the earth when the Messiah sets up his kingdom on earth (see commentary on Matt. 5:5: “the meek will inherit the earth”). Therefore, the Jews understanding of these concepts would not be based on a literal use of the word heaven in the sense that these physical things, namely, rewards, treasures, and homes, were actually in heaven, but rather, that God, who is in heaven, is “storing” them or keeping record of them. The actual receipt of these things will occur in the future on earth.
God is keeping records of the behavior of each person, a fact that is clearly stated in the Old Testament.
The “record books” of God are also mentioned in the book of Revelation. At the Judgment, “The books were opened” and “The dead were judged according to what they had done as recorded in the books” (Rev. 20:12).
Because the Old Testament said that God in heaven was recording people’s deeds, it was a common (and true!) concept in Judaism that people could add to that treasure by their good deeds.
“The notion of a heavenly treasure, beyond the reach of corruption, was a common eschatological concept in Judaism. The righteous on earth do not yet possess it, for it belongs to the future; nevertheless they can now add to it” (J. Emerton, C. Cranfield, and G. Stanton, The International Critical Commentary: Matthew).
“An important concept in Jewish and Christian theology is the belief that sins and virtues accumulate and are “stored” the way money might be stored in a treasury. The Lord was believed to keep records of every sin and virtue and require the books be balanced from time to time” (George Wesley Buchanan, The Anchor Bible: To the Hebrews; p. xxv).
The Jews in Christ’s audience knew that God was keeping track of their deeds with the intention of rewarding them. They will receive what is rightfully theirs when the Messiah returns and establishes his Kingdom on earth.