The Balaam story sets up the conflict between the religious and military powers of the ancient world and the seemingly simple word of blessing in the mouth of God. Neither the military might of Moab nor the terrible curses and divinations of ancient religion can thwart God's promise to bless God's people. The blessing of God will prove stronger than all contenders (see Numbers 23:23). Here is an early form of the ongoing biblical notion of God's strength through weakness, that God's word of promise is stronger and more trustworthy than all the powers of the world and the forces of human religion.
The rationale given here for God's fidelity to the promise is that "God is not a human being," not "a mortal." Thus, God will not lie (as a human might!). In Hebrew, God is neither an 'ish (a man, a male, a husband, a human) nor a ben-'adam (a "son of Adam," a member of the human species). That God is not a male human being is seen as good news. The Bible knows that no "likeness"--not that "of male or female"--can depict or capture God. God is rather present, as God chooses to be, in God's word (Deuteronomy 4:12, 15-18); here, in Balaam's oracle of blessing, it is that word of divine promise that will determine Israel's future. Hosea, too, knew that God was "no mortal" (that is, not an 'ish), also recognizing that to be good news, for it was a mark of God's gracious holiness that would not subject Israel to wrath.
19 God is not a human being, that he should lie,
or a mortal, that he should change his mind.
Has he promised, and will he not do it?
Has he spoken, and will he not fulfil it?
New Revised Standard Version Bible: Anglicized Edition, copyright © 1989, 1995 National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved worldwide. http://nrsvbibles.org