1)
How did Pharaoh refute Yisrael's claim?
1.
Seforno: Attributing their claim to sacrifice to their G-d, to laziness, he countered that he increased their burden in order to encourage them to work.
2)
Why did Pharaoh repeat the word "Nirpim"?
1.
Oznayim la'Torah: Firstly, he accused the officers of not beating the slaves who were lax in their work, or of not handing in the names of the slaves who did not fulfill their quota of bricks; 1 and secondly, he accused the Jewish slaves of being lax in their work.
1
For which they (the officers) were beaten.
