Hashem promised the Jewish nation that if they receive the Torah (19:5), והייתם לי סגולה מכל העמים, "You shall be for the most beloved treasure of all nations."
A segulah reminds us of the nekudah "segal," which is the formation of three dots (two on top and one beneath). The uniqueness of a segal is that even when it lies on its side, it remains a segal. Any way you turn it, it remains a segal. None of the other nekudos have this trait. Therefore, Hashem says, והייתם לי סגולה, you will be like a segal. This means that even if you fall, you will always remain the am segulah, the precious nation of Hashem.
Tefillah
At Matan Torah it states (20:15) וכל העם ראים את הקולת, "And the entire nation saw the voices." The Birkas Avraham zt'l says that the קולות can be referring to the voices of tefillah of Bnei Yisroel. It was at matan Torah that the Yidden thought back and realized how much they accomplished with their tefillos. They davened in Mitzrayim and shouted to Hashem. There were times when it seemed their tefillos weren't heard in heaven because their suffering continued. But now they were free men, they received the holy Torah from Hashem, וכל העם ראים את הקולת, now they saw what their tefillos accomplished!
About kriyas Yam Suf, it states (Shemos 15:21) ותען להם מרים שירו לה' כי גאה... Miriam called to the Jewish women, telling them to sing to Hashem for the miracles. ותען can also mean "to answer." ותען להם מרים can be translated as Miriam answered the women's question. They were asking, "What is the purpose of tefillah? We daven a lot, and we don't see results." ותען להם מרים, Miriam replied, "Now you see the miracles of kriyas Yam Suf. Now you see what we accomplished with our tefillos!" This is what the Jewish nation recognized by matan Torah. וכל העם ראים את הקולת, they saw what they accomplished with their many tefillos.
The Meor Einayim zt'l teaches that a quota of tefillos is needed before one receives his yeshuah. Sometimes we daven and think our tefillos aren't accomplishing, but each tefillah brings salvation nearer. Perhaps just one more tefillah is needed, and the salvation will come.
It also depends on the intensity of the tefillah. A tefillah said with kavanah will bring the yeshuah quicker. A mashal is a person who bangs a table. The table doesn't break. He can hit the table a thousand times, but the table remains firm and complete. However, one strong blow with a hammer and the table collapses. So, too, a strong tefillah with kavanah can accomplish a lot.
The second of the Aseres HaDibros is (20:3) לא יהיה לך אלהים אחרים על פני. This is not an easy phrase to translate. Many think that it means, "You shall not have other gods..." but that would imply that there are other gods, chalilah. As Rashi writes, "It is a disgrace for Heaven to call them gods along with Him." Rather, אלהים אחרים means that others call them gods. Rashi's second interpretation is that אלהים אחרים means gods who are strangers. Rashi explains, "For they are strangers to their worshippers. They cry out to them, but they do not answer them, and it appears as if the god were a stranger who never knew [the worshipper]."
The Imrei Emes zt'l said that if a person davens and thinks that Hashem won't answer him, he has chalilah made Hashem into a stranger, אלהים אחרים.
This is a very sharp vort. If one doesn't believe that tefillah helps, if he thinks Hashem isn't interested, he has made Hashem on the level of the אלהים אחרים, gods who are stranger to those who serve them.
In Tehillim (81:10) יהיה לא קל זר בך, and the Kotzker zt'l explains that Hashem shouldn't be a stranger to us. We should recognize that Hashem listens to us, is interested in us, and answers our tefillos. Hashem isn't אלהים אחרים, a stranger to us, disinterested in our requests.
