Or HaChaim on Genesis 37:5/אור החיים על בראשית ל״ז:ה׳

1 ויחלום יוסף חלום. Joseph had a dream. Why did Joseph add to his brothers' hatred of him by telling them of his grandiose dreams? Furthermore, knowing as he did that the brothers hated him fiercely, why did he accept his father's mission (verse 14) and venture "into the lion's den?" (According to Bereshit Rabbah 84,11 even Jacob could not understand Joseph's preparedness to accept his mission) Perhaps Joseph went to tell his brothers that they were wrong in ascribing his dreams to his ambitions, but that for some resaon G'd planned to elevate him to a high position and that Jacob's agreeing to send him on this mission was a sign that all of this had been approved by G'd. He may have hoped to assuage their hatred of him by accepting the misssion.

2On the other hand, he may have warned them that the time would come when they would have need of him, and that they might do better to suppress their hatred of him pending further developments; otherwise they would expose themselves to retaliation on his part when the time came. He was convinced that the brothers would accept what seemed to them a heavenly decree.

3There is yet another possibility. Joseph actually hoped to draw his brothers' hearts nearer to him. We have a saying Berachot 55 that כל החלומות הולכים אחר הפה, that "all dreams follow the mouth." [What the interpreter sees in the dream determines its true meaning. The reader is referred to an excellent analysis of this statement by Rabbi Yitzchak Arama in chapter 29 of his Akeydat Yitzchak, see my translation page 247, second edition. Ed.] The rabbis also say that one should enquire from someone who is well disposed towards him when searching for the meaning of one's dream (Rosh on that paragraph). Joseph hoped that by telling the brothers of his dreams they would themselves find an acceptable and plausible explanation which would put their minds at ease. At least they would realise that Joseph had no ambition to become king over them. Why else would he be silly enough to provoke their hatred by telling them about his dreams? All of this might have worked if the existing hatred had not already closed the brothers' minds to any conciliatory gestures.

4ויחלום יוסף Joseph dreamed. The Torah reports that Joseph only dreamed so that we should not think that he hallucinated making himself believe he had dreamed when in fact he entertained thoughts of lording it over his brothers. The reason that in verse 9 the Torah repeats again that Joseph dreamed is also to emphasise that it was a nocturnal vision, that he had not made up the story he told his brothers.

5ויגד לאחיו. He told his brothers. It was a good dream. The brothers were tough as nails and did not even want to know what he had dreamed; this is why he had to say: "please listen to the dream I have dreamed." I am sure that the Torah does not here refer to a dream the content of which has not been mentioned, nor to a dream which did not come true. If the latter, why mention the existence of such a dream? If to tell us that the brothers hated him even more, this too has already been adequately explained. We must therefore assume that these words refer to the dream Joseph revealed only after having insisted that the brothers listen to his dream.