Today, 23 Shvat, is the 113th Yahrzeit of Reb Yehoshua ben Reb Sholom of Belz ZY'A. For more information on this tzadik see http://en.wikipedia.org/wiki/Yehoshua_Rokeach
Here is a vort the Imrei Chaim quuotes from him on Parshas Bo:
The posuk says "And you shall tell into the ears of your son and your son’s son what I have wrought upon Mitzraim, and My signs which I have done among them, and you shall know that I am Hashem".
Why does the posuk starts off telling us to tell over what happened in Mitzraim, in the plural, but ends saying “you shall know that I am Hashem”, in the singular? Reb Yehoshua of Belz answers that when you speak to someone about emunah or the like, if you don’t feel it yourself than the message can’t be given properly, however if it comes from the heart then it will go into the other person’s heart. Therefore, it says “you shall know that I am Hashem” in the singular so that you will internalize that belief and will then be able to tell over properly what happened in Mitzraim.