Why does Yosef emphasize that his mouth was speaking to them?
(45,12) “And behold, your eyes see, as well as the eyes of my brother Binyamin, that it is my mouth speaking to you. And you shall tell my father all my honour…”
Behold, this posuk does not seem to have any relevance here, nor is its meaning very clear. It would have been better to write this above, when Yosef told them to tell their father “Hashem has made me a lord over all the Egyptians”. There it would be relevant to continue “you shall tell my father all my honour in Egypt…”.
But behold, on the posuk in Shir Hashirim 1:2 “Let him kiss me with the kisses of his mouth”, Rashi explained that it was the mouth that was saying this. But is it not obvious that it was the mouth that was speaking and not some other organ! However, Rashi continued there, that the kiss that the posuk was talking about was mouth to mouth, like a bride and bridegroom. But how did Rashi know this - maybe the kiss was on the back of the hand or on the shoulder? It was for this reason that he prefaced his explanation and said that the mouth was saying this. That is, the mouth was saying to another mouth "kiss me", and so the kiss of the posuk was clearly mouth to mouth.
Here too, we can explain in a similar fashion. Because it says in the Midrash (concerning the many items and honours that Pharaoh gave to Yosef) that because of his mouth that never kissed in sin (with the wife of Potiphar), he merited that “through your mouth you will nourish all my people” (Bereishis 41:40). This is what Yosef was saying: “it is my mouth speaking to you, and you shall tell my father all my honour”. It is my mouth, speaking about itself, that is saying “you shall tell my father my honour”, that I still remain righteous. Therefore, “you shall bring my father down here”.
Why didn’t Ya’akov also warn his sons not to engage in halachic discussion on the way?
(45,24) “And he sent off his brothers, and they went, and he said to them: אל תרגזו בדרך”
Rashi explains the last words of this posuk to mean "do not engage in a halachic discussion lest the way cause you to stray". Rather, you should hasten to my father. The question is asked why Ya’akov didn’t also warn them when they went to Egypt not to engage in a halachic discussion - surely he also wanted them to come quickly?
But the rule is that the mitzvah of learning Torah is greater than the mitzvah of honouring one’s father and mother. This we learn from the fact that Ya’akov was punished measure for measure for the twenty-two years that he delayed in the house of Lavan by Yosef being missing from him for twenty-two years, and thus he did not receive honour from him during that time. But for the fourteen years that he learned Torah in the Yeshivas of Shem and Ever he was not punished.
However, on the way to Egypt they did not know yet that Yosef was still alive, and so they thought that Ya’akov was being punished also for the fourteen years that he had spent in the Yeshivas of Shem and Ever. If so, honouring one’s parents was greater than learning Torah, and so they knew by themselves that it was forbidden to engage in Torah and thus not be involved in honouring their father and mother. Therefore, Ya’akov did not need to warn them not to delay on the way.
But now they saw that Yosef was alive, and if so, Ya’akov was only punished for the twenty-two years that he delayed in the house of Lavan, and not for the fourteen years that he had learned Torah. If so, they now realised that learning Torah was greater than honouring one’s parents. Because of this, Yosef needed to warn them not to engage in halachic discussion, but rather to hurry home in order to revive the spirit of their father, Ya’akov.
How did Ya’akov know that Yosef had remained righteous in Egypt?
(45,27) “And they told him all Yosef’s words that he had said to them, and he saw the wagons that Yosef had sent to carry him, and the spirit of their father Ya’akov was revived.”
The Midrash comments on our posuk “and he saw the wagons”, that he saw (prophetically) the covered wagons that the chieftains of the tribes would bring to the Mishkan, as it says in Bamidbar 7:3 “six covered wagons”. Immediately, “the spirit of their father Ya’akov was revived”, and he saw that Yosef was still righteous. This Midrash is a puzzle.
But behold, it says in the gemora Shabbos 49b that the thirty-nine forbidden labours of Shabbos correspond to the thirty-nine times the words מלאכה מלאכתו מלאכת appear in the Torah. But the gemora has a question whether the posuk in Shemos 36:7 “the work was sufficient” is included in this count because it means that they did the work just right, for example, flattening the golden plates so that they were neither too thick nor too thin. And if so, the posuk in Bereishis 39:11 “and he came to the house to do his work” is not included in the count, because it means that he entered to do what he needed with the wife of Potiphar. Or maybe this posuk is included in the count, because it means that he entered to do actual work, but the posuk “and the work was sufficient” is not included because it means merely that the work was complete. See there.
Now, it says in the Midrash that the chieftains of the tribes, regarding the contributions to the building of the Mishkan, said to let Yisrael donate first, and whatever is missing they will complete. But when they saw that the work was sufficient, that it was completed and nothing was missing from what was needed to complete the building of the Mishkan, they donated wagons.
Now we understand the Midrash that we brought above, that when Ya’akov saw that the chieftains would bring wagons, perforce the posuk “the work was sufficient” means that the work was completed, and therefore it is not included in the count of thirty-nine. That means that the posuk concerning Yosef “and he came to the house to do his work” is included in the count, and it means actual work. Therefore, Ya’akov exclaimed "Enough! My son Yosef is alive" - he is still righteous, because it is now clear that he did not sin with Potiphar’s wife.