Or HaChaim on Exodus 5:11/אור החיים על שמות ה׳:י״א

1 כי אין נגרע מעבודתכם, "for your workload will not be diminished." Why did the taskmasters say: כי אין נגרע "for it will not be reduced" instead of ואין נגרע? "and it will not be reduced?" When the taskmasters had first said: "go and get your own straw," the Israelites had thought of this as a welcome diversion. They considered collecting straw as less demanding than either building, or forming bricks. The taskmasters "dropped the second shoe" by adding that it was not as the Israelites thought that collecting straw was instead of their other work; rather it was in addition to their regular work. They explained that the reason for the decree was precisely so as not to diminish the Israelites' workload.