The Torah tells us, “And you must do this service in this month….”
The month of Nissan is a special month for the Jews, because of Passover and the several Commandments that Hashem gave us during that month. We received the Commandment of Bris Milah (Circumcision), which is a pivotal Covenant, our mutual agreement with Hashem. Those few Commandments that are called “Bris,” define us as Hashem’s Chosen.
Some of those are: keeping Shabbos, Milah, worshiping only Hashem and not one or more false gods, marrying only another Jew (whether born Jewish or properly converted to Judaism), and possibly some others.
We did not receive those last two in Egypt. However, during all the time we lived in Egypt no Jew ever married a non-Jew without a complete conversion. And while many of the Jews did worship idols for a while in Egypt, only those who made an effort to stop doing so were allowed to leave Egypt. The rest died secretly, during the Plague of Darkness.
We also received the Commandment of Shabbos during the month of Nissan, after we left Egypt, and also the Commandment of purification through the Ashes of a Red Calf (Rashi, Shemos 15:225, s.v. Shom Som Lo).
The Month of Nissan is sort of a minor Holiday. and there are several Laws and Customs that we keep during that month. There are some minor deletions in the Prayers, and one or two extra things we say.
If there is, Heaven forbid, a funeral during the month of Nissan, we may not say a eulogy, except for a great Torah Scholar. We do not establish a fast day or a day of mourning for the month of Nissan.
There are some exceptions to this. For example, all first born Jewish males must fast on the day before Passover.
Also, a bride and groom fast on the day of their wedding, as usual.
There used to be a Custom to fast on the day of a yartzeit (anniversary of a death) of one’s parent, and some people still do this, but this is not done during Nisan.
During the month of Nissan we should also visit blossoming fruit trees, and recite the special Blessing for such a sight.
And, perhaps most importantly, we are required to provide the poor with their Passover needs.
Each Jewish community is obligated to organize a charity drive for this purpose. It is called “Ma’os Chittim,” which literally means “wheat money.” In the Jerusalem Talmud it is called “kimche d’Pischa,” Passover flour. In other words, money for matzah. But the money is not limited to such purposes; it should help the poor buy whatever they need for Passover.
Some 100 years ago or more, someone once came to a Rabbi (I think it was Rabbi Yisrael Salanter, but I’m not sure), and asked him a Halachic question. If he can’t afford to buy wine for Passover, may he use milk for the Four Cups? (During the Seder the first two nights of Passover we must drink four cups of wine scattered throughout the proceedings. One at the beginning, one after explaining the Story of the Exodus, one after the Holiday Meal, and one after reciting the Hallel — Psalms of praises.)
Rabbi Salanter gave the man twenty-five rubles (Russian money of the time).
After the man had left, the Rabbi’s wife asked the Rabbi, “Since when does wine cost twenty-five rubles? Five rubles wouldn’t have been enough?”
The Rabbi answered, “If he wanted to drink milk, that means he didn’t have enough money for chicken or meat for the Holiday Meal either!”
Eating chicken or meat at the Holiday Meals are also a required part of the Holiday (unless it makes one sick). And we are required to do what we can to help the poor with ALL their needs.
Therefore, the Halachah says that the community must organize a Ma’os Chittim drive, and each person who lives in that town must contibute to it. That money may come out of one’s regular tithing (charity consisting of a tenth of one’s income).
One cannot be said to have truly and properly prepared for Passover unless one has also helped prepare for someone ELSE’S Passover as well, one way or another.