For I the LORD do not change; therefore you, O sons of Jacob, are not consumed. [Mal. 3:6]There are certain conclusions about the atonement that follow from this, and although I suspect that I'll have more to say about it later (this year? if I start reading Anselm before 2010?) Pelikan has a succinct summary about the matter.
Although it was customary in the language of the church to say that God 'has redeemed us from sins and from His wrath and from hell and from the power of the devil,' this needed to be understood in relation to the concept of 'rightness.' God did not require satisfaction as a means of appeasing his wrath, for he was impassible and therefore could not be wrathful as men are. Instead of speaking of the 'wrath' of God, therefore, Anselm spoke of his justice: the justice of God had been violated by the failure of man to render to God what he owed Him; the justice of God also made it impossible for God to forgive this sin by mere fiat, for this would have been a violation of the very order in the universe that God had to uphold to be consistent with himself and with his justice. Any scheme of human salvation, therefore, had to be one that would render 'satisfaction' to divine justice and leave the 'rightness' and moral order intact. [Pelikan, The Growth of Medieval Theology, 140f.]From this we may see something that I've discussed before: what we believe about God has consequences how we think about other things - in this case, the nature of the atonement. This dogma concerning God's nature also must necessarily inform how we read the Bible: if God is impassible - if he does not change - then we must conclude that passages that "literally" seem to say otherwise speak only anthropomorphically about him - describing God's actions in human terms. This reminds us again of why it is important to "read the Scripture within the living Tradition of the whole Church" (CCC §113).