"Halfway though the night, G‑d smote all the firstborn." (Ex. 12:29)

Rabbi Shimon stated: Come and see. It is written [here], "Halfway through the night," but it should have said, "around halfway through the night" or "around midnight," like Moses had said [to Pharaoh: "G‑d said: Around midnight I will go out in the midst of Egypt…." (Ex. 11:4)]

…so that Pharaoh's astrologers won't say that Moses is a fraud.

Our colleagues explained this as follows: [Moses said, "around midnight] so that Pharaoh's astrologers won't say that Moses is a fraud."

If they miscalculated the stroke of midnight, they would declare that Moses had lied, and therefore he warned them that the plague would begin "around midnight".

But nevertheless, the question remains because then the verse could have said: "And Moses said: around midnight…" - without saying it in G‑d's name, or stating an exact time. But since he made this declaration in G‑d's name, they wouldn't have said anything about Moses, but about his Master.

However, this is a mystical issue…. Until the night divided, the judgment was not made. From where do we know this? From Abraham, as it is written, "He divided the night against them". (Gen. 14:15)

The verse is usually translated as: "He divided [his forces] against them [and attacked] that night." However, if we translate the verse literally, following the order of the words, it would read: "He divided against them the night." Hence Rabbi Shimon's interpretation.

So this verse as well [should be interpreted as:] "at the division of the night," [in other words] "when He divided the night." Moses knew that G‑d would not make judgments until He had divided the night. And so indeed it was - He did not make His judgments until He had divided the night, and then He made His judgments in the second half of the night. This is why the verse states, "Halfway through the night…" [that is to say] in the second half of the night.

...the same aspect that smote the Egyptians rescued the Israelites….

The explanation is as follows: Do not think that the Holy Blessed One made judgments against the Egyptians with the strict severities of malchut (which dominates the first half of the night, as darkness increases until midnight), while He showed compassion for the Israelites with the aspect of tiferet (also called "compassion", which dominates the second half of the night, as night begins to change to morning). Rather, the same aspect that smote the Egyptians rescued the Israelites. And therefore the judgment only began at midnight, not earlier, for the Egyptians were deserving of death not only from the point of view of strict justice (malchut), but even from the point of view of compassion (tiferet).(Ohr Hachama)

[Zohar II:36a; translation and commentary by Moshe Miller
First published by Fiftieth Gate Publications and Seminars]