וַיֶּעְתַּר יִצְחָק לַה' לְנֹכַח אִשְׁתּוֹ כִּי עֲקָרָה הִיא וַיֵּעָתֶר לוֹ ה' וַתַּהַר רִבְקָה אִשְׁתּוֹ
The Gemoroh in Yevomos [64:1] explains that the Tefilos of Tzaddikim are like a fork to turn over wheat, etc. they can turn the will of Hashem from Middas hadin to middas horachamim [judgment to mercy]. Explains Rav Moshe Minder ZY"A [of Chasidei Slonim], how is this so? He answers, since Tzaddikim change their ways and wills, for the better, to serve Hashem, so too, can they change the will of Hashem.
Hashem listens to his Tefilos - of Yitzchok Avienu, says R' Yitzchok of Vorkoh ZY"A, that the Tefilos of Yitzchok were answered since they were with happiness, in contrast to Rivkah Eimeinu's, that were with sadness. Such is the strength of Simchah.
The Ohev Yisroel ZY"A says that the reason why Yitzchok Avienu's Tefilos were answered, since they were on the Tzar - pain, of the Shechinoh. Therefore, they were helped. From this we can learn the power of Tefilloh (prayer) and praise to Hashem.
The Tiferes Shlomo says that Hashem is כביכול a Yosheiv Tehillos Yisroel. He is sitting on the praises of Klall Yisroel. Just as a son-in-law "Zitzst oif kest" [Sits on dowery], so too, Hashem has a Nachas Ruach from the Tefillos and praises of Klall Yisroel.
This Shabbos ב' כסלו is the Yohrtzeit of the Yosher Divrei Emes. In his Sefer, he brings the following point that is relevant to every days Davening. Not to minimize it Chas ViSholom, but he speaks about those who are very lengthy in the added Piyutim of Tefillos Rosh Hashanah and Yom Kippur. But forget about the parts of Davening we say daily all year, sometimes hastily, unfortunately. "They are leaving the main part and dwelling, only on the secondary, which is also very important."
