שמות ט:כז פירוש: רמב״ן, רשב״ם, טור הארוך ורבנו בחיי

I HAVE SINNED THIS TIME. The explanation thereof is: “This time I will acknowledge the Eternal,²²¹See Ramban above, 8:15, that throughout, Pharaoh did not acknowledge the Eternal, the G-d of Israel. Ramban points out that this was the first time Pharaoh did acknowledge Him. Ramban transposes the words, chatathi hapa’am Hashem hatzadik, and explains them as follows: “This time I acknowledge the Eternal, for I have sinned against Him, etc.” for I have sinned against Him, and He is the righteous One, and I and my people are wicked, for we have rebelled against His word from then until now.”

חטאתי הפעם, now, this time I admit that I have sinned.

ה' הצדיק, “the Lord is righteous;” a reference to the warning issued by G’d to Pharaoh. When human beings exact vengeance they do not, as a rule, first warn the victim and provide him with a means to escape the impact of the punishment.