Instead of arranging for Yitzhak to become blind so as to enable Rivka and Yakov to trick him into blessing Yakov, G-d could have simply revealed Esav’s wickedness and unworthiness to Yitzhak. G-d would not have been divulging anything that Yitzhak didn’t already suspect of his son–after all, Yitzhak already knew that Esav’s wives were idolaters (although he excused his son by saying that he could not control his wives) and that he did not usually mention G-d in his conversation. G-d’s reticence here teaches us an important lesson: if G-d chose to allow Yitzhak to go blind rather than speak negatively about the wicked Esav, certainly we must take extreme care not to speak negatively of others. – Lubavitcher Rebbe