Source: Based on Likutei Sichos of the Lubavitcher Rebbe Vol. XV
"The Rebbe's Treasure: Interpretations of Talmudic Stories"
The Talmud [Sukah 29a] states that eclipses are bad signs for the world. The Talmud then elaborates on what can cause an eclipse:
An eclipse of the sun occurs for the following four reasons: For not having eulogized a chief judge (a chief judge is comparable to the sun, for he enlightens and clarifies things for the community - Maharsha); for not having helped a betrothed maiden when she called for help (to save her from ill treatment); for committing adultery and for killing two brothers on the same day.
Because of the following four reasons the moon and the stars eclipsed:
For committing forgery, for false witnesses, for raising sheep and goats in the land of Israel (that is, for letting goats and sheep pasture from other people's fields - Rashi), and for cutting down fruit-bearing trees.
The Shaloh [Noach p.274b] explains that seeing the lunar eclipse implies a bad sign. Hashem would ascertain that the Jews would see it if they were sinning. However, if they were not sinning, Hashem would darken the sky so that the eclipse would not be visible.
This interpretation is not satisfactory, for the Talmud states: "For the following reasons an eclipse occurs and not an eclipse is seen". The very occurrence of an eclipse is a consequence of the aforementioned sins and not the sight of the eclipse. Furthermore, in cloudless locations such as Egypt [see Rashi Vayigash 47:10 and Vaera 7:17] the Jews would always be capable of seeing the eclipse regardless of their behaviour.
The Rebbe's Commentary:
How can we say that something as natural and predictable as an eclipse can have an affect on people's welfare? Furthermore, how can we say that the actions of people can provoke the occurrence of something that takes place as regularly and naturally as an eclipse?
It is a wellknown fact that Torah scholars had a vast knowledge of science in general and astronomy in particular. Astronomy was very important for the Jews in order to establish the calendar and proclaim the new months. Even great non-Jewish individuals would ask the Rabbis scientific questions. Therefore, we cannot say that the Rabbis were uttering nonsense when it came to the subject of the eclipse.
Mazal - or constellation - occurs when the stars are in a certain position. Some days or times are auspicious for a good mazal, others are known to be times in which misfortune could happen, G-d forbid, due to the unfavorable mazal. So at certain moments, the mazalot can have influence on the people. Even the day on which one is born has an influence on his characteristics (Shabbat 126a). Therefore, specific mazalot provide people with good or bad tendencies. (Nevertheless, the Rambam in Hilchot Teshuva 5:4 says that a person is not controlled by his natural tendencies and he has the power to change them)
During the time of an eclipse, the stars are in a position that can have a bad influence on the people. At such a time, the four aforementioned sins are more readily transgressed! For this reason the eclipse is a bad sign for the Jews, because they are more likely to sin than at some other time. As a result, they might be punished. Hence it is not our actions that cause the eclipse, but rather the eclipse that can alter our actions, triggering a heavenly punishment.
Therefore, if Jews are doing Hashem's will, the effects of the eclipse will not concern them. Chazal even say that we should not worry about the influence of stars if we do what Hashem wants. For as long as we do not let the bad mazal alter our actions, we do not deserve any punishment.
Jews are not limited by the boundaries of nature, including the celestial bodies. We have the power to change our mazal by doing good deeds. Our mazal depends on our actions and our prayers.