Douglas Harper's Etymology Dictionary
1862, from modern Hebrew mazzal tob "good luck," from Hebrew mazzaloth (plural) "constellations."
Wiktionary
interj. (non-gloss definition: Used to express congratulations or good wishes, especially at weddings.) (qualifier: in a Jewish context)
Wikipedia
"Mazel tov" or "mazal tov" ( Hebrew/ Yiddish: מזל טוב, Hebrew: mazal tov; Yiddish: mazel tov; lit. "good luck") is a Jewish phrase used to express congratulations for a happy and significant occasion or event.
Mazel-tov ( Yiddish: מזל טוב, Yiddish: mazel tov; Russian title either «Мазлтов» or «Поздравляем», 1889), is a one-act Yiddish-language play by Sholem Aleichem. The play focuses on the relationship between the servants downstairs, the cook Beyle, and the upstairs rich, the Landlord. One memorable servant song from the 1889 play "Bitter is the food That gets burnt, Bitter is it to work Beyond your strength", was later recycled and included into the 1949 and 1969 Polish Jewish State Theatre production of The Treasure in the mouth of another servant, Zelda. The play was revived after the Revolution among the repertoire of the Moscow Yiddish Chamber Theater (GOSET) in the 1920s. It was set as an opera Congratulations! (Russian: «Поздравляем!» , Op. 111) by Mieczysław Weinberg in 1975.
Usage examples of "mazel tov".
When the coronation was over a wedding party was scheduled to hold a reception there, so the walls were draped in white bunting and repulsive little cherubs, and there was a big sign hung on the wall that said Mazel Tov!