"And they shall be mine, saith the LORD of hosts, in that day when I make up my jewels; and I will spare them, as a man spareth his own son that serveth him." (Malachi 3:17)
The jewels of the Lord are not rubies and diamonds, but rather are "they that feared the LORD" and who "spake often one to another." Instead of being mounted in a crown or other adornment as precious stones would be, these jewels will be listed in a very special book. "A book of remembrance was written before him for them that feared the LORD, and that thought upon his name" (v.16). What a blessing it would be if, when we get to heaven, we should find our names written in that special book of God's memories! God does take note of our times of spiritual fellowship with other believers—especially, no doubt, when they occur during times of stress and worldly opposition.
This word (Hebrew cegullah) is not the usual word for "jewels," more commonly being rendered "peculiar treasures." For example, Psalm 135:4 says that "the LORD hath chosen Jacob unto himself, and Israel for his peculiar treasure." The word suggests treasure carefully guarded in a safe place. The word is translated simply "special" in Deuteronomy 7:6, "a special people unto himself."
Note in particular Exodus 19:5-6: "Now therefore, if ye will obey my voice indeed, and keep my covenant, then ye shall be a peculiar treasure unto me above all people: for all the earth is mine: And ye shall be unto me a kingdom of priests, and an holy nation."
Peter uses the same language in writing to prepare Christians for imminent times of persecution. "But ye are a chosen generation, a royal priesthood, an holy nation, a peculiar people; that ye should shew forth the praises of him who hath called you out of darkness into his marvellous light" (1 Peter 2:9). HMM