A Rod Of Iron

Perhaps it refers to Christ, and perhaps not, but someone referred to as God's Son/son (the capitalization is ambiguous) is spoken of as ruling the nations with an iron scepter in Psalm 2:7-12.  A more popularly recognizable translation might be "a rod of iron."  Addressed to the church in Thyatira, Revelation 3:26-27 certainly applies this to general Christians, quoting Psalm 2's iron rod comment and referring to their rulership as an extension of the authority Jesus has received from Yahweh.  This broadness might not be the primary intention behind or emphasis in the original passage.  Still, it is said in the New Testament to parallel something that Jesus reserves for righteous people other than himself.  This reigning connects with far more of Biblical philosophy than just the triumphant words of Psalm 2.

Just as Paul says that Christians will eventually judge the world and angels (1 Corinthians 6:2-3) and Jesus tells parables that imply his followers will rule over regions after his return (Luke 19:11-27), Revelation 20 mentions those who participate in first resurrection, the resurrection of the righteous (Daniel 12:2, 1 Thessalonians 4:13-18), reigning with Christ after the Second Coming.  This is when the righteous or redeemed dead are resurrected from the unconsciousness of Sheol (Job 3:11-19, Psalm 6:5), not before the beast of Revelation 13 appears in what some call the Tribulation, or else the first resurrection would not be the first one at all.  These revived men and women rule alongside or underneath Christ as his priests and judges for a thousand years (Revelation 20:4-6).

As for what this reigning would entail, the only way to rule over nations in a righteous manner is to abide by the obligations and penalties of Mosaic Law, God's revelation of what justice is for a variety of sins and situations which does not change (Deuteronomy 4:5-8, Matthew 5:17-19, Malachi 3:6) because the divine nature they reflect does not change.  Justice, to give only some examples, is paying poor laborers their wages the very day of their work (Deuteronomy 24:14-15) and putting slave traders (Exodus 21:16) and idolaters to death (Revelation 17:2-7).  This is how Christians would rule the nations on Christ's behalf, carrying out the obligations rooted in God's nature with whatever firmness they call for.  As if Yahweh not changing and being the grounding of righteousness is not enough, Jesus affirms Mosaic Law on many occasions in the gospel accounts (besides the other passage cited from Matthew, another highly relevant one is found in Matthew 15).

To judge and rule with Jesus would by necessity involve enforcing the commands of the Torah wherever they are not bound in their context to particular times—for instance, Deuteronomy's commands to kill the Canaanites in the Promised Land could not be applicable to future followers of Yahweh after the inhabitants were already killed.  It is over and over stated in the Bible that the righteous will rule as part of their reward from God.  The Bible gives many examples in the Torah of what this would look like.  At this time, heaven has not yet come to Earth (Revelation 3:12, 21:1-4); there are still sinners that deserve terrestrial punishment within the boundaries of God's laws.

Ruling with a rod/scepter of iron within these precise boundaries of true justice would never overpunish.  There are always limitations on this (see Deuteronomy 25:1-3, Exodus 21:22-25, or Exodus 22:3 combined with Deuteronomy 15:12-14), some that exclude entire means of torture that have been rather fundamental to the practice of pagan or secular nations up to the present day.  To punish with physical torment when that is not prescribed could only be unjust and a betrayal of Yahweh's nature.  To use means of corporal or capital or also financial punishment that go beyond what is commanded, especially when it is rigidly prescribed to never exceed them (Deuteronomy 25:3), is evil.  Within the scope of Biblical morality, anything that does not contradict the objective boundaries is not unjust.  The reign of Christians and of Christ in the thousand years would not be one where the general brutality and arrogance of unbiblical governments is continued, for a rod of iron in the intended sense is not cruel.