God is not a man, that he should lie; neither the son of man, that he should repent: hath he said, and shall he not do it? or hath he spoken, and shall he not make it good?
In studying any attribute, the essential oneness of all the attributes soon becomes apparent. We see… that if God is self-existent He must be also self-sufficient; and if He has power He, being infinite, must have all power. If He possesses knowledge, His infinitude assures us that He possesses all knowledge. Similarly, His immutability presupposes His faithfulness. If He is unchanging, it follows that He could not be unfaithful, since that would require Him to change. Any failure within the divine character would argue imperfection and, since God is perfect, it could not occur. Thus the attributes explain each other and prove that they are but glimpses the mind enjoys of the absolutely perfect Godhead.
All of God’s acts are consistent with all of His attributes. No attribute contradicts any other, but all harmonize and blend into each other in the infinite abyss of the Godhead. All that God does agrees with all that God is, and being and doing are one in Him….
God, being who He is, cannot cease to be what He is, and being what He is, He cannot act out of character with Himself. He is at once faithful and immutable, so all His words and acts must be and must remain faithful. KOH122-123
What confidence that inspires, Lord! Thank You for Your faithfulness, love and unchanging nature. Amen. 
19 The words “God is not a man, that he should lie” describe both the immutability of the Lord and the integrity of his word. Balaam is himself a foil for God. Balaam is constantly shifting, prevaricating, equivocating, changing—he is himself the prime example of the distinction between God and humanity.
God is not a man, that he is able to lie,
Nor is he human, that he is able to change;
Has he said, and will he not do it?
Or has he spoken, and will he not confirm it?
Again two lines of bicolon mark this verse (4:2 and 4:3 meter), with the pairs enhancing each other. Balaam’s view of gods was based on his own human failings. Now he confronts God, who is not at all like humans in their failures. This fact is the stunning reality. All others may change; God—even with all of his power—cannot change, for he cannot deny himself (cf. 1 Sa 15:29; Ps 89:35–37; Heb 6:16–18). God must fulfill his promise, for he has bound his character to his Word.
23:19 God is not man, that he should lie. Balaam, even against his selfish intentions, must speak God’s truth (cf. v. 26). Here he is affirming that God’s truthfulness in general (cf. Titus 1:2; Heb. 6:18; God does not lie, and he cannot lie, for this would be contrary to his character) implies that his promises to Israel will also come to pass.
23:19 that he should change his mind Indicates that God will not change something He has decreed or promised. See 1 Sam 15:29, 35; Exod 32:9–14; Jonah 3:10. The message for Balak is that nothing he does will induce God to permit Balaam to curse Israel. Despite this message, Balak will move Balaam again after this oracle, still hoping for a different outcome (Num 23:27–28).
23:19 God is not a man. In contrast to the unreliability of man, so well seen in Balaam himself, God is reliable and immutable. He does not change; therefore, His words always come to pass.
 Tozer, A. W., & Eggert, R. (2015). Tozer on the almighty god: a 365-day devotional. Chicago, IL: Moody Publishers.
 Allen, R. B. (2012). Numbers. In T. Longman III & D. E. Garland (Eds.), The Expositor’s Bible Commentary: Numbers–Ruth (Revised Edition) (Vol. 2, p. 321). Grand Rapids, MI: Zondervan.
 Crossway Bibles. (2008). The ESV Study Bible (p. 304). Wheaton, IL: Crossway Bibles.
 Barry, J. D., Mangum, D., Brown, D. R., Heiser, M. S., Custis, M., Ritzema, E., … Bomar, D. (2012, 2016). Faithlife Study Bible (Nu 23:19). Bellingham, WA: Lexham Press.
 MacArthur, J. F., Jr. (2006). The MacArthur study Bible: New American Standard Bible. (Nu 23:19). Nashville, TN: Thomas Nelson Publishers.