John asks in the Open Theism Facebook group:
Ok in OT God doesn’t know the future. So how can God know what’s best? Can he make a mistake? Did he make a mistake? And did he make a mistake in the Bible?
The answer is pretty simple, actually. When someone else is to blame, then it is not your mistake. If I hire a worker and 10 years down the road they go through a painful divorce and shoot up the office, then it is not “my mistake” because I hired that worker. Nothing that I did could be considered unreasonable by normal standards and definitely could not be predicted. Mistakes may have been made, but the fault would not be with me.
But what if I ran a background check on the man and it turned out that he was just released from prison for shooting up an office. In that case, I may have made a huge mistake. Because I was negligent and should have acted wiser, the blame falls on me for the office shooting. Of course, the shooter has the moral culpability. But I would have made a mistake in putting all employees at risk.
There is a distinct difference between the two scenarios. When God repents of making Saul King, when God repents of making man, the only real way that would be a mistake is if God had reasonable knowledge beforehand that events would turn out the way they did. In other words, the only way that God would have made a mistake is if God knew the future.