What is the book of remembrance (Malachi 3:16)?

Publication’s description

Malachi 3:16–18 says, “Then those who feared the LORD spoke to one another, and the LORD gave attention and heard it, and a book of remembrance was written before Him for those who fear the LORD and who esteem His name. ‘They will be Mine,’ says the LORD of hosts, ‘on the day that I prepare My own possession, and I will spare them as a man spares his own son who serves him. So you will again distinguish between the righteous and the wicked, between one who serves God and one who does not serve Him.’”