When a child is born and at a wedding, people wish the baalei simchah "mazal tov." So, apparently, the concept of mazal applies to Klal Yisrael. Furthermore, the Gemara (Moed Kattan 28.) states, "ומזוני חיי בני, children, life, and parnassah are determined by mazal." Yet, the Gemara (Shabbos 156.) also says, לישראל מזל אין, that Yidden aren't under the influence of the mazal. So, which one is it? Are they under the influence of the mazalos or not?
Tosfos writes that both statements are true. Yidden have a mazal, but it can changed by performing great mitzvos. Tosfos writes, משתנה גדול זכות ידי על, through a great merit, his mazal can change.
This topic is related to this week's parashah, because Avraham said to Hashem (15:2-3) זרע נתתה לא לי הן ...ערירי הולך ואנכי לי תתן מה אתי יורש ביתי בן והנה, "What will You give me, since I am going childless... Behold, You have given me no seed, and behold, one of my household will inherit me."
Rashi and the Gemara (Shabbos 156.) add that Avraham said, "I see in the stars (mazalos) that I am not able to bear children." Knowing astrology, Avram saw no hope for him to bear children.
The Gemara (Shabbos 156.) says that Hashem told Avraham, "Go away from your astronomy because לישראל מזל אין, Bnei Yisrael aren't tied down to the mazal." Rashi (on the Gemara) explains, "With tefillah and merits, one's mazal can improve." Tosfos says that a great merit can change the mazal, and Rashi writes that tefillah can also change one's mazal.
What is an example of a great merit that can change one's mazal? The Chasam Sofer zt'l says that emunah is an example of a great merit.
Hashem told Avraham two things: that he will bear children, and his children will inherit Eretz Yisrael. Avraham believed he would have children, but he wasn't certain they would inherit Eretz Yisrael. For the inheritance of Eretz Yisrael, Avraham requested proof. Avraham said (15:8) אלקים 'ה אירשנה כי אדע במה, "Hashem, Elokim: How shall I know that I will inherit it?"
Why did Avraham believe for certain that he would bear children but wasn’t certain that his children would inherit the land?
The Chasam Sofer answers that attaining Eretz Yisrael depended on the Canaanites’ refrain from doing teshuvah. Avraham knew...
