In my opinion, when Joseph saw his brothers bowing to him, he remembered all his dreams, and knew that not one of them had been fulfilled, as he understood their interpretation - all of his brothers would bow to him would bow down to him in the beginning. Since Binyamin was not with them, he thought of this trick as an excuse to bring Binyamin with them, to fulfil the first dream first, and therefore for this reason he didn't unmask himself immediately and tell his father who he was. If it were not for this reason, Joseph would have sinned in a great way to cause his father such pain and mourning both on him and Shimon. Even if desired to hurt his brothers, how could not have compassion about his aged father?
However, Joseph did everything in its right idea in order to fulfil his dreams.
Rabbi Shimshon Refael Hirsch
We have an obligation to try and explain the behaviour of Yosef.
There as a possibility that Joseph should have admitted who he was to his brothers straight away, not only for the sake of his father. Especially when he recognised the hand of G-d in everything that had happened to him, and he learned to see his problems, including the sins of his brother against him - as a G-dly service in order to enrich him.
It is also impossible that such a wise and clever person like Joseph should believe that he has an obligation to set himself up as a conduit in order to fulfil his dreams. If there is importance to a dream, it is possible to leave its fulfilment in the hands of the One who sent it.
It is certain that these calculations were completely forced in order to bring Joseph into the actions that he took. Without it, it would appear that his behaviour was a bother without reason; and this is not within Joseph's character, both in terms of his wisdom which is unimpeachable. If we can stand in his shoes, we can arrive at the following explanation.
If it was the intention of Joseph to appear in his father and brothers eyes as a "Kosher" person, as a person who happens to rule, and if it were in his heart to return to his family as a son and brother, he would not have needed any of these tricks.
However, Joseph in the role of an Egyptian prince educated and brought up his sons according to the spirit of the house of Jacob. This Joseph, whose eyes always looked ahead, even to a time after his own passing, and commanded that that his bones should be brought to rest in the land of his fathers; that Joseph felt that he needed two changes to occour before he would be able to admit to his brother his true identity:
1. He would need to change his brothers' views regarding him. Their feelings regarding this needed to change completely, in order to establish a relationship of close brotherhood. If this would not be the case, even if Joseph would return to his family, his family would be lost to him, and he would be lost to them.
2. It is also only natural that Joseph also guarded a grudge in his heart regarding his brothers, and he remembered the hardness of their hearts and the time that they closed their ears from hearing his pleas in the pit, and they removed themselves from the pain that they would bring to their father (through selling him/killing him). These emotions could only be erased though a clear proof that his brothers had experienced complete regret for their actions.
He therefore had to place his brothers through a test, to see if they were capable of taking another son from their father - this time for indisputable reasons which were objectively creating hardships for them. Perhaps the possibility of life imprisonment, and the vision of a family falling apart from famine, should be substantial enough reasons to act in this way, rather than any imagined danger that appeared to them to arise from Joseph's pretentions to being a leader? From this perspective it was very neccesary for Joseph's feelings. Only if his brothers were able to stand against this, would he be able to chase from his heart the lingering bitterness he felt.
However, the second consideration, and perhaps the more important one, is that his brothers should change their view of him: Joseph remembered his dreams, and how they caused his brothers to be suspicious that he had desires of power - to the extent that they suspected danger to arrive from him towards them as a result. They saw themselves as within their rights to commit the greatest of crimes from a position of self defense. If that was the case when he was wearing his coat of many colours, how much more so should they have to fear from him now, not only because he is a "king" in reality, but also because he has a reason to dislike and hate them (they are spies/having stolen money from him/the cup of Joseph take your pick!) and is able to freely revenge himself on them as any noble is on low persons in his kingdom without power!
It was therefore needful for the brothers to recognise the true nature of Joseph, and for that it was needed - first and foremost to show himself to them as a true ruler. Until this moment, they could have thought of him as a "grocer" of produce. However, now, they had to present themselves to him as a ruler. They would be obligated to come to a recognition that he could do with them exactly as he wished; and despite this he would act kindly to them, and provide them with goodness, despite the badness that they had allegedly done to him. This would be the reason to hope that this would cure their emnity and mistaken ideas about him.
The bottom line is as follows: in the moment that he admitted that he was their brother Joseph, he would remove the blindness from their eyes, and it would be in the hands of Joseph and his brothers to completely erase the past. It is only in this way that Joseph could hope to return like a son to his father, and to a brother to the sons of his father.
If we haven't made a mistake thus far in our reasoning, it was those considerations that prevented Joseph from creating a link with his father during the years of plenty. What good would come to his father to have one son, but to lose 10 others, seeing the tension and the hatred which existed between them? Within this framework, all the tricks of Joseph were required and needful, and in our opinion are fitting to the wisdom of Joseph.
Any intelligent person should be surprised: Why did Joseph cause such pain to his brothers and his father?
The explanation of the Ramban who says that he did this in order to fulfil his dreams etc, (does not compute) because if the Almighty wants these dreams to be fulfilled, they will be, and Joseph shouldn't do anything?!
