Literally translated, this is what is commonly said in the Jewish community, upon hearing very good news (typically life-cycle events as such as engagement, marriage, birth).
"A good sign and a good constellation may it be for us and all of Israel". It is traditionally said in Kiddush Levanah (Blessing of the New Moon).
Hashem just blessed someone with a wonderful event, and our response is to give credit to signs and stars? Rambam explicitly forbids assigning beneficial traits to the stars in Hil. Avodat Kochavim 11:
"אֵיזֶהוּ מְעוֹנֵן אֵלּוּ נוֹתְנֵי עִתִּים שֶׁאוֹמְרִים בְּאִצְטַגְנִינוּת יוֹם פְּלוֹנִי טוֹב יוֹם פְּלוֹנִי רַע יוֹם פְּלוֹנִי רָאוּי לַעֲשׂוֹת בּוֹ מְלָאכָה פְּלוֹנִית שָׁנָה פְּלוֹנִית אוֹ חֹדֶשׁ פְּלוֹנִי רַע לְדָבָר פְּלוֹנִי: "
"Who is an observer of times [which is prohibited]? They that point at times, saying astrologically: "That day is a good one, that day is a bad one; that day is fit to do that particular work, but that year, or that month, is bad for that particular thing."
How did this strange phrase enter our vocabulary, and how is it Halachicly permissible to continue saying it?
NB: In this related question, one answer suggests that "Mazal" means "flow"; which I had never heard, and seems untenable in all other uses of the term (such as "Ein Mazal L'Yisrael")