The word of the LORD came to Samuel: "I regret that I have made Saul king, for he has turned back from following me and has not performed my commandments." (1 Samuel 15:10,11; ESV)
These verses refer to God's response to Saul's rebellion against him. Saul, the first king of Israel, began well, but as time went by tended to do things his own way rather that trusting in God and his Word. What God said to the prophet Samuel sounds as if God had second thoughts about making Saul king and that if he would have known that Saul would blow it the way he did, then he would have chosen someone else.
This is the kind of incident that someone might use to show that God is not omniscient. To say that God is omniscient is to say that he knows everything. But if he knows everything, how could he regret his own decision? Even if God purposely chose Saul knowing he would fail (which God did know), then would not his response be something more like "Did I not know that Saul would be unfaithful to me?", rather than something along the lines of "Oh no! What have I done?"
That God is omniscient is a given in the Scriptures. The Bible assumes that he is the Creator and Master of the Universe, who never loses control over his creation. It is on this basis that David, Saul's successor could write "Even before a word is on my tongue, behold, O LORD, you know it altogether" (Psalm 139:4; ESV).
But if God indeed knows everything in advance, then how could he "regret" that he made Saul king? The Hebrew word, translated here as "regret," is nacham. Interestingly this same word is used later on in this same Haftarah portion, where the prophet Samuel says to Saul, "And also the Glory of Israel will not lie or have regret, for he is not a man, that he should have regret (1 Samuel 15:29; ESV). It is helpful that this translation uses the exact same English word in each case, even though the Hebrew word may be understood differently in different contexts. It is better that we are left having to struggle with a supposed contradiction, than having the English translators resolve it for us.
The word nacham carries with it the idea of change. It has two primary meanings. The first is "to relent," which is a change of intension whereby one course of action is replaced by another. The other primary meaning is "to comfort" or "to be comforted". Here the change is an emotional one in which someone feels a certain way, usually bad, and is consoled, thus causing their outlook on life to change. An example of this use is found in Psalm 23, where we read, "your rod and your staff, they comfort me" (Psalm 23:4; ESV)
So nacham denotes what we might call a change of heart or mind. Our Haftarah portion, which uses the meaning of "relent" tells us that this is something that God both does and does not do. When Samuel says that God "is not a man, that he should have regret", he is saying that he is not fickle. He is absolutely dependable. His Word is true and his character is unchanging. He cannot and will not be manipulated by anyone or anything. Those who cooperate with him, stand in right relationship with him. Those who don't are alienated from him. As long as Saul stayed true to God, God was with him. But once Saul rebelled, God's relationship with him had to change.
When the Bible tells us that God relents or expresses regret, it is not saying that God made a mistake that he wishes he could have prevented. Rather, it is that he is grieved over a situation that necessitates a new course of action. Thankfully, this also works the other way. Saul's rebellious course typifies the state that we all as human beings find ourselves in, but a state in which we need not remain. Through turning from our rebellion and trusting in the Messiah Yeshua, we need not anticipate God's wrathful judgment. If we turn to him, he will relent. We can count on that!