Albert Barnes Commentary Malachi 3:17

"And they shall be mine, saith Jehovah of hosts, [even] mine own possession, in the day that I make; and I will spare them, as a man spareth his own son that serveth him." — Malachi 3:17 (ASV)

And they shall be Mine, says the Lord of hosts, in that day when I make up My jewels—this reflects the recurrence of the words עשה אני אשר יום (see Malachi 3:21 in Hebrew, which is Malachi 4:3 in English versions) and סגלה לי והייתם ; so we find both phrases elsewhere. In Deuteronomy 7:6, there is the equivalent לעם לו להיות סגלה, and similarly in Deuteronomy 14:2 and Psalm 135:4. Or perhaps better: “And they shall be to Me, says the Lord of hosts, in that day which I make (or, in which I do this) a special treasure.”

“In the day of judgment, those who fear Me and believe and maintain My providence shall be to Me a special treasure, that is, a people uniquely belonging and precious to Me, blessed in the vision and fruition of Me. For as in the old law, Israel was a special treasure, a special people and inheritance of God, chosen out of all nations, so in the new law, Christians, and those who are righteous through grace, are the special treasure of God, and in heaven shall be His special treasure in glory, possessed by God and possessing God.”

The “special treasure” is something much prized, greatly treasured, and guarded. Such are Christians, bought at a great price, even by the precious blood of Christ. But Malachi says they shall much more evidently be such in all eternity, which that day of final retribution shall decide, “joying in the participation of their Creator, by Whose eternity they are fixed, by Whose truth they are assured, by Whose gift they are holy.”

And I will spare them—this is a remarkable word, as used of those who should be to Him a “special treasure,” teaching that they shall be such, not by their own merits, but by His great mercy. It stands in contrast with the doom of the wicked, whom that day shall sentence to everlasting loss of God. Still, the saved also will have needed the tender mercy of God, by which He pardoned their misdeeds and had compassion on them: If Thou, Lord, shalt lay up iniquities, O Lord, who shall stand? (Psalms 130:3). Among those whom God will spare on that day will be countless individuals whom the self-righteous despised as sinners. “I will spare them, although formerly sinners; I will spare them, repenting, and serving Me with the service of a pious confession, as a man spares his own son who served him.” For our Lord says of the son who refused to go work in his Father’s vineyard, and afterward repented and went, that he did the will of his Father (Matthew 21:31).