These are the Ten Plagues which the Holy One, blessed be He, brought upon the Egyptians:
מכת בכורות חשך ארבה ברד שחין דבר ערוב כנים צפרדע דם
Rabbi Yehudah referred to them by acronyms: דצ"ך עד"ש באח"ב "ב ח א ב "ש ד ע "ך צ ד
Daas Zkeinim
The acronym is in order to understand the order of the warnings prior to the plague. The first plague of each set (1,4,7) the warning is to Paroh at the river. The second in each set (2,5,8) is to Paroh in the palace. The third in each set (3,6,9) was given without warning.
Ravan
The plagues were divided into three groups. The first three were done by Aharon with the staff. The second three were done by Moshe without the staff. And the third set of three were done by Moshe with a staff.
Maharil Diskin
First set of three plagues were of the earth below and the water; the second set involved in the air close to the earth; and the third set was in the sky close to the heavens
Malbim
First group of three expressed confirmation of G-d’s existence; the second group of three expressed confirmation of G-d’s Providence; and the third group of three expressed confirmation of G-d’s control of time, space & man
Alshich
First group of three came to confirm the existence of G-d; the second set came to confirm the unique bond between G-d and the Jews; and the third set came to confirm His complete rulership of all things
Klil Tiferes
The simanim come to indicate that the plagues were for the sake of the Jews דור צדיקים כשרים עם דעה שלימה בני אלקים ח יים בינה A generation of Kosher Tzadkim with complete knowledge children of G-d living understanding
The Russian government once requested that HaRav Yitzchok of Volozhin and the Rebbe HaRav Menachem Mendel of Lubavitch come to St. Petersburg, the capital, to answer many questions pertaining to Judaism. With HaShem's help, they succeeded in pleasing the government officials with their answers.
One day a Catholic priest approached them. The rabbonim were surrounded by many Russian ministers who had gathered to see whether or not the Jews could refute all the questions about Judaism. The priest brazenly said: "You Jews. You always say that you do not need human blood for Pesach, but I will show you in your own book that you all need blood!" While speaking he took out from under his coat a Haggadah Shel Pesach and pointed with his finger at the passage stating that R' Yehuda made mnemonic signs of the initials of the ten plagues: Detzach, Adash, BeAhav. The priest said that the initials stand for:
Dam tzerichim kulanu (ד ם צ רִ יכִים כּוּלָנוּ) — We all need blood —
al devar sheharagnu (ע ל ד בַר ש הָרַגְנוּ) — because we killed —
ben Ei-l chai bashamayim (ב ית א -ל ח י ב שָמַיִם) — the ‘son’ of the living god in heaven.”
"Now I want you to admit to me," said the priest, "that the Jews need blood on Pesach."
We can, of course, understand it being undesirable to admonish the priest for his warped pshat, nor answer him calmly with an explanation found in the commentaries, such as according to R' Ovadiah of Bartenura, R' Yehuda made mnemonic signs of the ten plagues to help him remember them. The priest would surely not accept that explanation despite it being true, since he was not seeking the truth but only to hurt the rabbonim and disgrace the Jews.
One of the Rabbis immediately devised a true answer that effectively closed the priest's mouth. “I will explain to you what the initials that R' Yehuda gave mean.
Dovrim tzorereinu kazav (דוֹבְרִ ים צ וֹרְ רֵינוּ כּ זָב) — Our enemies talk falsehood —
alilat dam sheker (ע לִילַת ד ם ש קר) — blood libels are false —
b’nei Avraham chalilah bezot (ב נֵי א בְרָהָם ח לִילָה ב זאֹת) - the children of Avraham would never do such a thing.”
Upon hearing this explanation HaRav Menachem Mendel expressed his agreement to prove it correct. They both looked at the bewildered priest who neither knew what to answer nor add to what he had previously said. (Mishel Ovos)
