Malachi 3:6
For I am the LORD, I change not; therefore ye sons of Jacob are not consumed.
For I am the Lord,.... Or Jehovah; a name peculiar to the most High, and so a proof of the deity of Christ, who here speaks; and is expressive of his being; of his self-existence; of his purity and simplicity; of his immensity and infinity; and of his eternity and sovereignty:
I change not; being the same today, yesterday, and forever; he changed not in his divine nature and personality by becoming man; he took that into union with him he had not before, but remained the same he ever was; nor did he change in his threatenings of destruction to the Jews, which came upon them according to his word; nor in his promises of his Spirit, and presence, and protection to his people; nor will he ever change in his love and affections to them; nor in the efficacy of his blood, sacrifice, and righteousness; wherefore, as this is introduced to assure the truth and certainty of what is said before, concerning his being a swift witness against the wicked, so also for the comfort of the saints, as follows. The Targum is,
"for I the Lord have not changed my covenant.''
therefore ye sons of Jacob are not consumed; such who were Israelites indeed, true believers in Christ; these were not consumed when the wicked Jews were, but were directed to leave the city before its destruction, and go to another place, as they did, whereby they were preserved; and so it was, that not one Christian perished in it;
See Gill on "Matthew 24:13" and so it is owing to the unchangeable love, grace, and power of Christ, that none of his perish internally or eternally, but have everlasting life.