At the end of last week's Parsha, Moshe asks Hashem a question: "Why have you dealt so harshly with this people?"(שמות ה:כ"ב). Moshe was really asking how Hashem could send him on a mission to ask Paroh to let the Jews go when that mission resulted in greater harm and suffering for the Jews. At the beginning of this week's Parsha, Hashem replies,"I am Hashem, and I appeared to Avraham, to Yitzchak, and to Yaakov using the name קל שקי, G-d Almighty, but my name יקוק, Hashem, I did not make known to them."(שמות ו:ב',ג') One interpretation of this answer is that Avraham, Yitzchak, and Yaakov underwent many trials and endured many deprivations, and yet they asked no questions of Hashem, never challenging His word or doubting His ability. According to this interpretation, Moshe was being told that our forefathers didn't question Hashem, so too he should not question the acts of Hashem. Only after Hashem teaches this lesson to Moshe does He go on speaking about the upcoming redemption.
Rashi makes an interesting point concerning this answer from Hashem, which further highlights the message of Mussar which Moshe was being given. He notes that to Avraham, Yitzchak, and Yaakov, Hashem revealed Himself using the name קל שקי, but to Moshe He reveals Himself as Hashem, יקוק. Rashi explains that the name שקי means the G-d who makes promises, but He had not yet fulfilled those promises. To Moshe, however, He used the full name Hashem, meaning the God who fulfills those promises. In other words, according to Rashi, Moshe was being told that the Avos never questioned Hashem, even though He did not fulfill the promises He made to them. Moshe, on the other hand, was about to see the fulfillment of Hashem's promises, as Bnai Yisrael prepared to leave Egypt. He certainly should not have questioned Hashem.
The difficulty is why Moshe Rabbeinu, who embodies the Middah of Chochmah, wisdom, even questions the actions of Hashem in the first place. Why would Moshe have any doubts at all and thus need to be rebuked by being compared to the Avos? The Lubavitcher Rebbe answers this by suggesting that
Moshe was neither doubting nor questioning the acts of Hashem. Rather, he was seeking an explanation for something which seemed to be incomprehensible to him. He simply wanted to understand Hashem's method of operation here and thus he asked, not doubting Hashem, but seeking greater understanding. Hashem's answer, then, was not a rebuke or a Mussar lesson, but rather an indirect response to Moshe's question. Moshe had asked why Hashem was doing what he was doing, and Hashem answered that His actions will become clear when He fulfills His promise, adding that this is how He dealt with the Avos. He made promises which would be fulfilled at a later time; now was that "later time" and the promises would be fulfilled and everything would make sense. We may learn from this that there is nothing wrong with asking a valid question about something we don't understand, but we must realize that we may not always receive a direct answer and thus will have to wait and see how things develop before we are fully satisfied with the response.