Or HaChaim on Exodus 6:9/אור החיים על שמות ו׳:ט׳

1 מקצר רות ומעבודה קשה, for impatience of spirit and cruel bondage. Perhaps the people did not respond positively to this assurance because they had not yet received the Torah. Since Torah broadens a person's mind, the Torah may hint at that by describing the Israelites' state of mind as "narrow minded, limited."

2ומעבודה קשה, and because of the cruel bondage. The reason that the Torah writes: "and because of the cruel bondage," is that they suffered from קצר רוח, impatience, quite independently of the effects of the bondage on their state of mind. They had become impatient at their fate when they pondered the additional workload Pharaoh had imposed upon them. A person who is in that frame of mind cannot even perform the labour he is normally capable of performing. This is why the Torah adds the words ומעבודה קשה.

3The people had good reason for becoming impatient at their fate because when Moses had come he had given them hope that their liberation was close at hand. This had given them a new and broader perspective on life. Now, when Pharaoh had decreed additional hardships their minds could concentrate only on how to cope with the immediate and even worse situation. The word מעבודה may therefore be understood as something comparative, i.e. the even greater bondage than had been their lot prior to Moses' coming.