Malachi 3:17–18 (ESV)

17 “They shall be mine, says the LORD of hosts, in the day when I make up my treasured possession, and I will spare them as a man spares his son who serves him.

In this passage, the reference to the day of the Lord and the coming judgment finds its fulfilment in the coming of Christ (Matthew 25:31–33), to whom the Father has given the authority to judge (John 5:22). Christ has received this authority as the reward for his redemptive work. He receives the power to give eternal life to those whom the Father has given him (John 17:2), those for whom he suffered and died. By giving judgment to Christ Jesus, the Father glorifies his Son and ensures that the Son receives the same honour as the Father (John 5:23). The coming day of judgment will not only serve to usher in the full salvation of the redeemed but will also bring great glory and honour to Christ.