Mattityahu 12:39-40

Orthodox Jewish Bible

³⁹ But Rebbe, Melech HaMoshiach answered them, Dor rah umnaef (an evil and adulterous generation) seeks for an ot (miraculous sign), but no ot will be given it except the ot of Yonah HaNavi.

⁴⁰ For just as Yonah was in the belly of the great fish SHLOSHAH YAMIM USHLOSHAH LAILAH (three days and three nights, YONAH 1:17), so will be the Ben HaAdam (Moshiach) in the heart of the earth SHLOSHAH YAMIM USHLOSHAH LAILOT (three days and three nights).