This parable can be found in Matthew 13:24-30 and its explanation is given in 13:36-43. It is often assumed that this parable is about the end of the world and the final judgment. My aim will be to demonstrate that this is not Jesus's main concern in the parable.
"The kingdom of heaven may be compared to a man who sowed good seed in his field." (v24)
The man is Jesus, as in all the other parables in Chapter 13, and the good seed is Israel, whom He planted in the world as his own people after the exile:
"I will appoint a place for My people Israel, and will plant them, so that they may dwell in their own place and not be moved again" (1 Chronicles 17:9)
"But... his enemy came and sowed tares among the wheat" (v25)
The enemy is the devil, who planted unbelieving Jews amongst the believing community. He sowed imposters who cared more about traditions than about a relationship with God.
"Allow both to grow together until the harvest" (v30)
The harvest is at the end of the age, that is, at the end of the Old Covenant age. Jesus is sending out his apostles (they are called "messengers" in the explanation) to bless and to curse, to gather up the righteous into the church and to condemn the apostate Jews to God's Judgement. That the harvest is inaugurated by Christ's ministry is clear from Matthew 9:35-38.
"First gather up the tares and bind them in bundles to burn them up" (v30)
The burning of the tares probably represents the siege of Jerusalem and the destruction of the temple in 70AD. This is Christ's act of judgement against the Jewish people for their rebellion against Him (compare Matthew 24:15-21 with Luke 21:20-24).
"Then the righteous will shine like the sun in the kingdom of their Father." (v43)
This is probably an allusion to Malachi 4, which is description of Christ's ministry, his first and not his second coming. This is clear from the fact that John the baptist (Malachi 4:5) is mentioned. The righteous shine like the "sun of righteousness" (Christ) as they trample down the wicked, conquering the nations by the power of the gospel (Malachi 4:2-3).
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