The Lord will spare them on the day.
This verse does not describe what they will be spared from, but in Malachi 4:1 where “the day” is mentioned, it is meant that those who fear the Lord will be spared the blazing anger of God in the judgment to come. God will spare them in the same way that a father spares his son who serves him, that is, an obedient son. The word translated “spare” means “to show pity to” or “to have compassion on.” The Lord will show no pity for the unfaithful of his people (Ezekiel 9:9–10), but the faithful will be spared.
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.