Ibn Ezra is often claimed as an example of an early Jewish Open Theist. John Sanders points to his commentary on Genesis 22:1 for evidence of this. Evidently, Sanders is referring to the following commentary:
Some say we need to read with different spelling: נשא instead of נסה ‘Uplifted’ instead of ‘Test’. And I say, the content of the Parashah (the story) proves that נסה is a ‘Test’. And experts explain that נסה (Test) means – to know what exists in the present. And the Gaon (a Babylonian Jewish leader) explained that the purpose of the test was to show His righteousness to the people. But the Gaon surely knew that when Avraham bound his son, no one else was there. And others say “go to the land of Moriah, and offer him there as a burnt offering on one of the heights” meant to be “make a sacrifice upon the mountain.” And not him for sacrifice. And Abraham did not know the secret of the prophecy, and he hurried to slaughter him, and God said to him, “I did not ask for this.” All these wise leaders needed their interpretations because they couldn’t believe that God would command a Mitzvah and then change it. But all those leaders did not notice that there is a precedent for a change like that. In the case of commanding a role for the first born male child (Bamidbar ג – Nombers 3) He replaces them with the Levites one year later. (And my understanding is) that the text of the Torah uses “נסה” Test, and that is why we don’t need to think that anything changed. God tested Avraham for the purpose of giving him a reward (and not for the purpose of commanding sacrifices or showing his righteousness).