We read about the akeida. Hashem tells Avraham what he wants from him. In 22:2 Hashem says, bring your son, etc.. " והעלהו שם לעולה" - bring him up there as a sacrifice.
Rashi already tells us that Hashem never said to actually slaughter Yitzchak. He only told him to bring Yitzchak up.
Did Avraham misunderstand Hashem and what He wanted? Did Avraham make a (nearly fatal) mistake?
I guess that for it to be a good test, Hashem had to find a way to say it ambiguously, using a word that implies offering it up for a korban but could be interpreted differently, so He could retract later. Avraham seems to have misinterpreted the ambiguity of God, but that was the point.