Musar su Levitico 19:26

“You shall not practice divination or soothsaying” (Leviticus 19:26). “You shall not practice divination” - such as those that divine with weasels and birds. [It is if] his bread fell from his mouth or a gazelle crossed his path, and he said it is a sign that his journey will not be successful - so he leaves his journey because of this. And that which is similar to this, such that he follow the augurs, whether to do something or to refrain from the action. “You shall not practice soothsaying (teonenu)” is an expression of times (onot) and hours: That he says, “Day x is good to begin work, hour y is bad for leaving.” And one should [also] not listen to the astrologers. But rather one’s heart should trust in the Lord, the God of the heavens and the God of the earth. Therefore it is written about this matter (Deuteronomy 18:13), “You must be wholehearted with the Lord, your God.” We have learned from this that the diviners and the augurs are lacking trust. And these plots and divinings are the acts of the Land of Canaan, as it is stated (Deuteronomy 18:14), “For those nations that you are about to dispossess do indeed resort to soothsayers and augurs; to you, however, the Lord, your God has not assigned the like.”

לא תנחשו . The reason for this prohibition is to teach us not to rely on falsehoods, nor to attribute events to coincidence. We must remain aware that G–d supervises His universe and exercises control. If we want to know something essential about the future we can consult the Hight Priest who will receive an answer from G–d via the אורים ותומים in his breastplate. Even the wicked Bileam realized that כי לא נחש ביעקב, that Israel's relationship with G–d is such that it does not need to resort to soothsaying and similar black magic.

Similar considerations are the reason why we must not consult cloud patterns. The overall lesson is that our fate hinges on our merits and not on the caprice of pre-determined times which by themselves influence our fate.