Bearing in mind that Pharaoh was speaking to Moshe and Aharon, why did he ask for forgiveness in the singular ("Sa")?
Ramban: It was a sign of the deep respect that he 1 had for Moshe, 2 whom he perceived as a god. 3
Ramban: As well as the whole of Egypt had - see 11:3.
Oznayim la'Torah: He nevertheless realized his mistake, and ended in the plural, "v'Ha'tiru El Hashem."
See the previous Pasuk (10:16), where he placed Moshe and Aharon on a par with Hashem, as he did again in this Pasuk; see Ramban. See also above 7:1.
Why did Pharaoh refer specifically to the plague of locusts as "ha'Maves ha'Zeh"?
Moshav Zekenim: Some explain that the Arbeh ate their faces and gouged out their eyes. This is death!
Refer to 10:16:1:2* and 10:16:1:5.
Maharal (Gevuros Hashem Ch. 33, p. 126): These last three Makos were more severe than the prior seven; they were all tantamount to death. Refer to 10:7:0.1:1; and to 7:14:7:2 and its notes. 1