The pasuk in this week’s sedra says: וישמע הכנעני מלך ערד ישב הנגב כי בא ישראל דרך האתרים וילחם בישראל וישב ממנו שבי – “The Canaanite, king of Arad... heard that Yisroel had come... and he warred against Yisroel.” Rashi explains that this was actually Amalek. They disguised their language to speak Canaanite to trick the Jews into praying for the wrong thing.
If Amalek knows the power of tefillah and the omnipotence of Hashem, why do they remain Amalek? The answer is that their sechel [intellect] may have told them the truth, but their tayvos [lusts] were not compatible with being a Jew. There is a long distance from a person’s brain to his heart.
This is the story with all of us. We know the emes, but from time to time, we do things that we should not be doing. There is a big difference between the sechel and the lev. Even when witnessing miracles, like water coming out of a rock, people can rationalize and deny if they want to continue living their current lifestyle. Our job is to see to it that our sechel overpowers our lev.