Why only now did Yisro bring Tzipporah back to Moshe?
(18,1) And Yisro the high priest of Midian, the father-in-law of Moshe, heard all that G-d (El-him) had done for Moshe and for Yisrael, His people, that Hashem had taken Yisrael out of Egypt. And Yisro, the father-in-law of Moshe, took Tzipporah, the wife of Moshe, after she had been sent away.
Why does the posuk say that Yisro "heard all that G-d (El-him) had done to Moshe" using the name El-him which signifies the attribute of justice, instead of using the name Hashem as it does at the end of the posuk?
But we can explain it according to the Yalkut on our posuk, which teaches that "after she was sent away" means after she was sent away from Moshe with a bill of divorce. And it is taught in the Midrash and the gemara, that at the burning bush the attribute of justice left its mark, and Moshe was punished by having the priesthood taken from him and given to Aharon.
According to this, this is the reading of the posuk: "and Yisro heard all that G-d had done for Moshe", all that the attribute of justice had done to Moshe, that the priesthood was taken from him. If so, it was permitted for him to remarry the wife whom he had divorced. Therefore, Yisro "took Tzipporah the wife of Moshe after she was sent away", because until now he was a priest and she was forbidden to him, since a priest may not marry a divorcee.
What did Moshe mean when he told Yisrael to be prepared for three days?
(19,15) He said to the people: Be prepared for three days.
Why did Moshe say here "be prepared for three days", instead of "be prepared for the third day", which is what Hashem had said?
But we can understand it according to what Rabbeinu Bachayei explained in the name of the Midrash, that Moshe made the sun stand still five times: at the Red Sea, when they travelled from Ramses, during the war with Amalek, at the giving of the Torah, and during the war of Arnon. And the gemara in Avodah Zorah 25b teaches that the duration of the standing of the sun was three days. (The gemara says 36 hours, which is three daylight periods, and thus three days).
Now, it is taught in the Midrash on parshas Bo that the posuk (12,2) "This month shall be to you", is explained by the posuk in Tehillim (72,7) "May the righteous flourish in his days, and abundance of peace until there is no moon". What is the connection between theses two posukim? And it says further in the Midrash that the month is thirty days and the kingdom of Yisrael is thirty generations, because the kings of Yisrael were like the days of a month. And yet it enumerates there that there were fifteen righteous kings and seventeen wicked kings, a total of thirty-two!
But according to what I wrote above the standing still of the sun caused one day to last for three days, and thus this month of Nisan in which they went out of Egypt had effectively 32 days. This is the meaning of the Midrash which said that "This month shall be to you" is explained by "May the righteous flourish in his days, and abundance of peace until there is no moon", that there was no ruling of the moon, but rather the night shone like day.
And this is also the meaning of the posuk (12,37) "And the children of Yisrael journeyed from Ramses to Succos", a distance of 120 mil, in one day. Because although the gemara in Pesachim teaches that the distance an average person can travel in one day is ten parsaos which is forty mil, since the sun stood still on that day, as Rabbeinu Bachayei taught, they travelled the distance of three days, which is 120 mil.
Now, Chazal taught that at the giving of the Torah, for every commandment that was spoken Yisrael went backward 12 mil. If so, for the ten commandments they went back 120 mil, and for this they needed three days as we wrote above. Because of this Moshe made the sun stand still on the day of the giving of the Torah for three days. This is what Moshe meant when he said in our posuk "Be prepared for three days" - be prepared for one day which will be as long as three days.